I just realized something about the Endgame trailer. This isn't spoilery, but I am fairly certain this is true, and it is in direction contradiction to what the trailer wants viewers to think. Using tiny font for people who wouldn't want to have figured this out, in the (IMO, very likely) event this ends up being true:
I think the footage of Scott in the trailer's stinger is NOT Scott after escaping the quantum realm. Rather, it is from before he went there in the first place. If I had to guess, I would say it is in the short timeframe between him being released from house arrest and the time we see him go into the quantum realm in the end-credits scene. But it doesn't really matter either way. So, contrary to what the Endgame trailer seems to want us to think, I don't think at all that that scene indicates that Scott escapes the quantum realm all on his own and shows up to save the day.
That scene is made out in the trailer to be HIGHLY significant. But it would not surprise me at all if it isn't really significant at all, or if its significance is something completely different than what the trailer implies.
A couple of other things I thought of:
Something is up with Tony's armor. The suit he has is nanotech. From everything we saw of it in Infinity War, it seemed like any damage could almost-instantly be repaired, provided there were sufficient nanoparts to cover that damaged area. So...why does the helmet Tony uses to record his message to Pepper appear to be so damaged and battered? Something different appears to have happened rather than Tony just being stranded on Benatar immediately after Infinity War.
And
Not related to the trailer, but...regarding the time stone: In the months after Infinity War, I have seen people note that the stone was glowing when Strange gave it to Thanos, indicating that it was somehow activated and doing something. I'm not so sure, but let's roll with that idea for a second. The theories I have seen about that are along the lines of the stone itself traveling through time, so that another version is sent backward or forward to some other point in time so that it could be given to the Avengers to stop Thanos. I have a slightly more mundane possible explanation. The stone was being used, but not for time travel--at least, not in the same sense. Going back to Strange viewing the 14 million scenarios, maybe what he was doing was actively using the stone at that point to continue viewing the scenarios so that he could continue guiding everything down the correct path that led to the only winning outcome. So, if true, he was actually using the stone to "travel," but not in reverse or at an accelerated pace or whatever. But was using it more to navigate through time at normal speed down all the branching possibilities and stay on the one path he wanted.