Some of the good guys die: This is a big, big, movie and the stakes have to be equally as big and I can't think of any better way to raise the stakes than by having several of the protagonists die in the course of the movie. This would also be an excellent way of ensuring people are invested in seeing Infinity War Part 2 when it comes out. Have Part 1 end with several of the big namers dead and people will buy tickets to see what happens in the second part. Obviously, none of the deaths would be permanent and would be reversed in the sequel.
The Mad Titan Triumphant: As above, have Infinity War Part 1 end with Thanos standing seemingly victorious over our heroes as a way to build anticipation for Part 2.
The movie will implode from the sheer number of Chrises: We've almost reached Christical mass!
Then suddenly...Adam Warlock!: I have to imagine that Warlock will be in either Part 1 or 2. They've hinted at his existence in the MCU in the Guardians of the Galaxy movies, he played a big part in the Infinity Gauntlet/Infinity War events in the comics, and he's like Thanos' #1 enemy, so he has to have a role in either movie. Personally, I'd save him for the second act with him only appearing at the end of the first.
Oh Captain, My Captain Marvel: I'm hoping Carol Danvers is in this somewhere. I know her movie is set in like the early 90s, but they could easily explain her lack of aging as being a side effect of her powers or whatever.
Tony will spend much of the movie trying to hire Shuri: Once he meets Wakanda's techno-whiz and sees all of the technology she's developed, I imagine he'll continually try and poach her with ever increasing salaries, titles, and perks.
Bucky Barnes' hair will look fabulous: The only prediction that will bear fruit because damn, that man has some nice hair. He had a lovely pornstache in I, Tonya too.
