John Murdoch
Senior Member
I think Steve for sure will be going home, I just don't know if it's in Infinity War or Avengers 4/The Film Formerly Known as Marvel's The Avengers: Infinity War - Part 2. Chris Evans' contract is about up, plus his death would thematically fit for the end of this MCU Avengers lineup (old school team leader who doesn't fit in the post-war world sacrificing himself, motivating one of his friends - Bucky or Sam - to take up his mantle).
Tony would be second; it again would signal the end of an era, paving the way in an almost meta sense for the audience to move on to the new Avengers lineup, as RDJ Iron Man has been the face of the MCU since his kick-off solo film a decade ago. Also, he could sacrifice himself to save the world and his comrades, something that would show how his character went from a self-centered, egotistical playboy to a someone willing to lay down his life for the world's safety.
Thor is also on my list, as his character and movies have been more about explaining the cosmic side of the MCU and pushing it forward (he was a walking plot device in Age of Ultron, Dark World introduced Aether, the Collector, and the fact that multiple Infinity Stones were being sought, Ragnarok mid-credits involved Thanos confronting the Asgardian refugee spaceship). Once Thanos is gone, Thor - and Asgard for that matter - might go with him.
Loki: see above.