Now first off, the sequel to Arkham City wouldn't be titled Arkham World because there is no way the entire planet would end up being turned into a prison but after playing Batman Arkham Origins, there is only one specific area in Gotham that the game creators in charge of the games have not done the official gameplay at.
the entire East section of Gotham City
and within that section of Gotham City is where the main events in that section will take place;
Wayne Tower
Wayne Tower is the largest building in East Gotham City and as big as it is, inside would have lots of places to wander through and for the tower to be where the main event in the game will take place at, one of Batman's foes along with a huge army of thugs would take over the whole building and use it for a base of operations throughout the city therefore the significance of the building would speculate the title of the next Arkham game as
Batman Arkham Tower
Now for the characters of the fourth game here are who we expect the game creators to use and who to voice them
Playable
Kevin Conroy will reprise his role as Batman
After dealing with the aftermath in Arkham City the dark knight returns once more to deal with any villains and gangsters that are still on the loose and must explain to his companions what he wouldn't talk to them about Talia al Ghul or Joker. After all, not all the games have to be about the Joker.
Colleen O'Shaughnessey to voice Zatana Zatara
Daughter to one of Bruce Wayne's mentors, Zatana was one of his love interests and as a magician, it would be a great idea to try playing out as a hero/heroine with more unique fighting abilities in the Arkhamverse. At first Zatana appeared on a poster in Jezebel Plaza in Batman Arkham Origins, but now it is time for the talented magician to put her skills to the test on helping Batman take down the bad guys in the game
Mark Rolston to reprise his role as Deathstroke
Deathstroke was one of the 8 assassins that Joker hired to kill Batman in the Arkham Origins and because of how big things are getting on the Suicide Squad, there is high speculation that Deathstroke might return with his team members joining him in battle
Robin and Nightwing will be playable only in the Challenge maps
Supporting Characters
Kimberly Brooks will reprise her role as Oracle
She helps Batman remotely on tasks he needs to do
David Kaye will reprise his role as Commissioner Gordon
Head of the GCPD and ally to Batman
Robert Costanzo will reprise his role as Harvey Bullock
The hothead who helps Gordon get the job done
Amanda Waller
Rick Flag
Cheshire
Cheshire's name was teased on a folder in Batman Arkham Origins. She will appear in the fourth game as a member of Amanda Weller's Suicide Squad
Deadshot
A supervillain marksman highly skilled in ricocheting gun shots, Deadshot was one of the assassins Joker hired to kill Batman and was smuggled into Arkham City to take out political prisoners who claim to be a threat to Hugo Strange. It is highly unlikely but as a member of the suicide squad in the sequel to Arkham City, Deadshot is likely to act as an ally to Batman but only this once.
Bronze Tiger
Another member of the Suicide Squad
Quincy Sharp
A man whose life as Warden of Arkham Asylum is now ruined because of the Joker beating his security with Harley Quinn's help of accessing the security overrides and whose life and reputation as mayor of Gotham is ruined by Hugo Strange acting mad with power over Arkham City falsely arresting innocent people with evidence against him and for letting the inmates kill each other with illegally smuggled weapons. Whatever Sharp will be doing now after these events will be decided by the people in charge of the next game if they are up to having it planned as Arkham City's official sequel.
Villains and Adversaries
Brian Bloom will reprise his role as Black Mask
Black Mask aka Roman Sionis was once Gotham's most powerful crime lord before the Joker came into Gotham and made his life a living hell by killing his girlfriend Tiffany Ambrose in his safe house at Lacey Towers, turning most of his men on him, robbing his bank, and torturing him for days. Now that with Joker dead, and his operations crippled, Roman would now be able to take back everything that the clown stole from him except for his dead girlfriend and as desperate as he is on regaining control over Gotham now that Joker, Penguin, Two Face and many other competative gang leaders are out of the way, and by taking control of the Wayne Tower and getting most of his operations set back up there, he will serve as the main antagonist (for real this time) in the whole game. And while taking control of the tower, Black Mask will be sure to have most of the criminals in Gotham obeying him as their new boss because of how many who survived the aftermath of Protocol 10 have grown tired and stressed out from taking orders from loud yelling crazies like Harley Quinn, the Penguin, and Two Face that some of them are wanting to get a break from crime and many of them are more than happy to work for someone who is not so psychotic so that they can go back to having an easier life for themselves just the way they were before Joker and many supervillains in town and out of town showed up and since Black Mask is the only sane crime lord who still stands, he would be sure enough to have most of the criminals carrying out his operations throughout the city.
Hush
After somehow escaping from Arkham City, Hush is for revenge against Bruce Wayne for unknown reasons. The cliffhanger to Hush's escape his one of the many reasons why a sequel to Arkham City has to be developed and to why Wayne Tower would serve as one of the 4th game's primary locations and to why the 4th game's title should be Arkham Tower because with Hush impersonating Batman's true alter ego, it would be very interesting to see what sinister crimes he might commit, maybe even be having Black Mask take control of the Tower which would make people in Gotham go blaming Bruce Wayne for Black Mask's mad scheme, and even more to make Wayne suffer as much as he has.
Tony Todd to voice Killer Croc
As one of Batman's most dangerous enemies, Croc was one of the eight assassins hired to kill Batman in the Dark Knight's second year of crime fighting and was last seen in the sewers of Arkham City which indicates that he may still be at large. In this possible upcoming video game sequel, Croc would appear as one of Roman Sionis' top hit men, killing anyone who opposes him or rejects taking orders from him and in return, Sionis would let Croc do what ever he want's with his victims. Croc would also act as one of the final bosses of the game's main story as well.
Scarecrow
Another villain whose fate is still unknown after the incidents in Arkham Asylum and Arkham City, Scarecrow would also be another villain available for return in the Arkham City sequel since he wasn't present in Arkham City, it was assumed that Crane made it out of prison alive which means he'll be back to terrorize Gotham once more. He maybe included as a side mission boss.
JB Blanc to reprise his role as Bane
Bane is one of Batman's toughest and most relentless foes. Since he is still obsessed with wanting to kill Batman, he may return as boss of the main story as one of Black Mask's hit men or a side mission.
Now for some new villains to expect in the game
Phosphorus Rex
As one of Batman's least popular enemies, Phosphorus Rex would serve as one of Black Mask's top hit men and a potential adversary to the Bat. He might serve as a boss for Zatanna to fight against in the game.
Steve Blum to voice Man Bat
A fierce were bat, Man-Bat would take flight in the game as a villain for Batman to take on in a boss fight similar to Firefly in Arkham Origins.
Robin Atkin Downes to voiceThe Werewolf
One of the lesser known villains in the Batman comics, the Werewolf would serve as a boss for Batman and Deathstroke to fight.
other returning villains involve
Poison Ivy
Poison Ivy is one of Batman's female enemies expected to return for the 4th game. After Catwoman turned down on retrieving the last of a certain plant species , Ivy is now angrier than ever and will be attempting to kill all humans on Earth as long as her obsession with plants remains. She will act as one of the bosses for Zatanna to fight in the game.
Harley Quinn
The Joker's girlfriend whose operations are now brought down by her apprehention in Arkham City will be expected to be taken hostage by Black Mask who will intend on killing her to even his score with Joker for killing his girlfriend.
The Penguin
The psychotic little arms dealer whose crime operations have been crippled by his defeat in Arkham City and now has less much henchmen working for him now.
The Riddler
No Arkham game is complete without having the villain in charge of the bonus items spread out throughout the city included so Riddler will be back as well.
Many enemies of the game will involve mobsters, criminals, martial artists and enforcers. All voice actors from Arkham Origins who voiced them will reprise their roles
To find out if all of these characters will turn up, stay tuned for any updates that come.