Spoiler Thread: Avengers Infinity War
The Russos keep saying no though.
Yeah, I'd imagine, from the director's experience, they don't really want a major plot device to be dependent on a different movie. I know this is a "culmination of things", so some of that is out the window, but even Infinity War gave brief commentary on how everyone got there. Gamora talks about her relationship with Thanos, and Thanos and Gamora have various scenes outlining it (so, you didn't need to see GotG). Quill mentions he had to kill his dad, who killed his mom. Thor talks about his issues in the past. Strange mentions he guards the time stone.
There are various examples, where a quick one liner gives you the min background you need, but if you watched the movies, you understand a lot more.
I think the Quantum realm alone will allow Antman to travel back in time or something, if he ends up in Captain Marvel.