Re: Characters you'd like to see in future Avengers movies?
If you want to introduce Ultron, the continuity already contains one "genius" who's inventions routinely fail in spectacularly dangerous ways: Justin Hammer. You got to figure if that guy ever tried to replicate Jarvis, he's pretty much guaranteed to end up with Ultron. I'd love to see Rockwell in a sequel. Supposedly, he's not in Iron Man 3.
"I just need to upgrade the AI a little so I don't have to... Oops."
Jensen Ackles for MCU Venom!
Spider-Man (2017): His MCU solo debut. The film would star Vulture as the villain, hired by Kingpin to stop the new hero, and take Peter back to high school. Eddie Brock would be introduced as well.