1. Besides Batman: Arkham Asylum, the Joker has been getting so much of the spotlight since Arkham City
2. Because of the plot twist in Arkham Origins, it made Joker steal the spotlight from Black Mask as the main villain just by having to have impersonated the crime lord the whole time on the game's main story plot that just makes more of the video game franchise all about him that they all thought it was just not enough for the Joker to appear as the game's secondary or tertiary villain on Batman's first encounter with him they had to make him steal the show which is why we do not want him returning alive in Batman Arkham Knight
3. Even though Joker is a great villain as well as Batman's arch enemy, the fact that he keeps on taking the spotlight as in being the one responsible for every plot that Batman must thwart through out most of the games is like the people who make these games are too obsessed with the clown that they just don't get that we all had enough of him.
4. One Arkham Game without the Joker involved would help make things in the Arkham Games much less irritating and because Joker is dead after having his last attempts for a cure to his titan disease was provoked by Batman and because of how the twist in Arkham Origins of him commiting the main plot of the game while pretending to be Black Mask, there is no way Batman Arkham Knight is gonna bring him back alive having him impersonate Scarecrow or be the Arkham Knight's true identity, otherwise it's gonna make some of the fans come after the people in charge for not giving it a rest with the Joker already and not to mention that the Arkhamverse will be more refered to as the Jokerverse since the games heavily revolve around the character.
5. If the Joker is to show up in Arkham Knight, he is best to work secretly with Scarecrow, Arkham Knight along with Harley Quinn and two of his Arkham City gang rivals secretly without being seen with the gang until later or just appear as one of Scarecrow's nightmare illusions and not physically return alive at all so that it won't be so f-ing irritating at all.
6. One very good reason why Rocksteady would certainly not bring Joker back to life despite the rumors of the studio spilling the beans other than because of the clown being the reason Arkham City along with other catastrophic events happening in the Arkhamverse is because of the point of view speech Batman had made as his final words to Joker "You want to know something funny? Even after everything you've done, I would have saved you." So clearly that is one other sign of proof that Joker will not return in Arkham Knight and would only be mentioned and seen throughout Scarecrow's nightmare illusions.
7. One good reason Rocksteady would not make Joker come back to life impersonating Scarecrow like he did pretending to be Blackmask is because Scarecrow is also capable of being just as unpredictable as Joker and since he has been capable of inflicting Batman with his worst fear, reliving the events of his parent's death, he will return as the real Johnathan Crane who survived Killer Croc at Arkham Asylum and proof that Joker is not going to be impersonating Scarecrow throughout the game other than Joker not wanting to team up with his rivals and with Scarecrow having Harley, Penguin, and Two Face work together with him and the Arkham Knight against Batman is the difference with their right eyes and when Joker died, both his eyes were evenly alligned as Scarecrows eyes were not evened up which shows that he had been disfigured since his encounter with Killer Croc.
8. And for why Joker cannot be the identity of the Arkham Knight is that with the Arkham Knight being highly skilled in matial arts techniques as Batman and for how he was said to be an exclusively original character, Joker's chances of spoiling everything are 25%
9. And because Batman: Arkham Knight is the final chapter of the Arkhamverse, Joker's death marks it only the beginning of the end so if he was brought back to life, then Arkham Knight wouldn't be the end of the Arkham games at all
To find out for sure if the rumors on Joker's return are just a hoax or not, stay tuned for the release of Batman: Arkham Knight in June 2015