Given how Avengers: Infinity War ended, it should come as no surprise that the directors are currently doing as much as they can to protect the somewhat inevitable spoiler that Thanos' snap will be undone one way or another in Avengers 4.
Their favourite mantra seems to be that anything can happen in the MCU and no matter how unexpected it would be for some of the "dead" characters in Infinity War to stay dead, that's very much the message they're trying to put out.
The latest stage of that agenda has just hit the net courtesy of the Huffington Post, who the Russos told that the upcoming MCU sequels don't necessarily mean that any of the characters in them can't be killed permanently. Most interestingly, they focused specifically upon the Guardians of the Galaxy, whose third movie so far hasn't been announced as following on from Avengers 4 in the timeline. According to Anthony:
“Here’s the thing, I think it’s important to remember anything is possible in the MCU. Just because there’s a sequel on the books doesn’t mean … people become accustomed to time moving linearly in the MCU. That doesn’t necessarily have to be the case. There’s a lot of very inventive ways of where the story can go from here.”
And Joe added to that sentiment:
“There’s four years between Guardians 2 and Infinity War. That’s a long time, and a lot of Guardians stories to tell. Again, as Anthony said, don’t expect everything to move forward in a linear fashion in the Marvel universe.”
That might seem like they're just clawing at a means to preserve the Infinity War ending's impact, but they raise an interesting point here that could mean something else entirely. As they confirm that the third Guardians movie could come between Vol 2 and Infinity War, that means Adam Warlock's involvement in it could actually lead into the Infinity Gauntlet saga and could give Marvel a means to tie him to the Stones as he is in the comics.
Perhaps we could see the relationship between Warlock and the Soul World - and the Stone, of course - that is such an important part of the Infinity Gauntlet comic arc? Perhaps the events of Vol 3 could directly lead into the character being imprisoned on Soul World, where he could meet the newly imprisoned Gamora and plot a means to undo Thanos' snap?
There has to be a reason why the Russos so clearly stated the difference in time setting and the relation to the Guardians and this would definitely work.