My first bet's on either Cap or Stark, and whichever one dies, the other must live
I'm leaning towards Cap dying, as we see an older Stark in the Avengers 4 pictures
I reckon Vision's gotta die, having the Mind Stone ripped out of his head has at least gotta weaken him to a breaking point
Thor's a bit of a 50/50 imo, on one hand he's more or less served his purpose to the series, but on the other there's no doubt he'd be a pretty sick survivor, as the king of Asgard's people (if Asgard's people still exists of course)
Also an addendum to that guess - if Korg dies we riot
Doctor Strange, Spider-Man, Ant-Man, Scarlet Witch, Black Panther and Starlord are pretty much confirmed to survive until at least phase 4, I could include Black Widow but her future film could very well be set in the past, sorta like Captain Marvel
I don't know how on EARTH Hulk is gonna be killed off, since he's pretty much invincible, so I'm guessing he'll survive until at least next movie, 'course Mr "Snap my fingers and kill everyone" might have something to say about that so I dunno
I'm confident that Nebula will die, based on what we see from the trailers and the fact that she has a blind vendetta to kill Thanos, no doubt she'll get in waaaaaay over her head and get killed by Thanos early on
Hawk-eye - I don't know whether they're saving his larger role until next movie, but I think he'll get killed off early on, which is why we don't see much from him in the trailers
There's something in the back of my mind telling me that Drax is gonna kick it, I really hope not, but it looks like it could happen, for reasons similar to Nebula's
Rocket and Groot will survive, I'm confident about that, they wouldn't kill off Rocket because of the comedies, and Groot's already died once so killing him off again is kinda like shitting into the wind at this rate
Mantis won't die, they've introduced her too late to kill her off now
Gamora, I don't think she'll die, she's one of Thanos' children but she's got the common sense to stay out of his way, then again it could be a good send off for her
Collector's dead, he's got the Reality Stone, those sneak previews are suggesting he's gonna die before he gives up the stone
Loki will likely side with Thanos for the beginning part, but will put himself before Thor to save Thanos' life, so I think Loki's going to die
Falcon I reckon will survive, and will be around after Cap's eventual death to take up the mantle (since Bucky's taking up the White Wolf mantle)
With that, Bucky will most likely survive too, however I think there's a chance he could die saving Cap's life or vice versa, it's about 60/40 on Bucky surviving
Rhodey's looking a little worse for wear, I'm worried about him, and I think he might die in battle, relates back to his Civil War quote "Every single one of those flights could've been my last, but I flew 'em."
No doubt Shuri will survive, for Okoye I'm not too certain, seems like she would also die for her country, it could be a fitting death for her character
I honestly think that Heimdall has/is the Soul Stone, his character has been around for that long, and I think he's going to die
Wong I don't know, it seems like he has a small enough role that his character could die, but then again he could give so much more to the franchise, so 50/50 on his end
Everyone else is a 50/50 as well imo, but only because I don't know enough about there roles in the story to make a judgement just yet