Now that "Ant-Man" has hit theaters, Phase 2 of the Marvel Cinematic Universe (MCU) is complete. While Phase 2 was all about the exploits of Marvel superheroes, Phase 3 is going to be about the aftermath, and that means heavy shiz is going down.
Things get started with a big conflict between Iron Man and Captain America in "Captain America: Civil War," which premieres May 2016; following that, "Thor: Ragnarok" will probably lay waste to Asgard; and that's all before Thanos, the purple dude who has been teased since the first "Avengers," raises hell in the "Avengers: Infinity War" movies. And if these films are anything like their comic counterparts, the MCU is about to get insane.
They are Just Speculations :
1. Thor might kill an Avenger.
In Marvel comics he has killed a character named Goliath who can change its size on his will but that Thor was created as a cyborg clone by Iron man. It will happen because we know that captain america civil war is going to give us hints about "Thor: Ragnarok," Also we will see destruction of another character
2. Ant-man
And as we know with the death of Quicksilver in Avengers age of ultron Marvel has made clear that it will not fear killing off a character so Ant man will replace the killed Avenger and he could be killed after by Ragnarok.
or It may be
3. Falcon
As Director has told reporters that there are more to Ant man's story so it may not be Ant man it could be Falcon instead. As there are no plans from Marvel to create a standalone film for Falcon so he may be the candidate and as Foster was killed from Captain america team. falcon could be killed from iron man's team.
4. Evil-Vision
As we already know Vision is also creation of Iron man he played part in creating him somehow so it may happen that if marvel has decided to bring Ragnarok in the captain america next movie so it will happen that vision will be the one to converted to Ragnarok.
5. some dead villains will return
6. End of Captain America
he was assasinated by carter and crossbones after he surrendered in comics so may be in the movie too will be killed.
7. Superhero Cameos
With marvel's superhero universe extending too much we will see many superhero cameos including some from fantastic Four Team also.
Some of the credit goes to huffington post for this.