Well, if someone else hypothetically gets control of the infinity gauntlet, they could snap their fingers at the very end and bring everyone back. The other option is that they destroy the infinity gauntlet and effectively reset the entire universe to zero, or create the cinematic version of the Marvel Multi-verse, allowing for new adaptations of Marvel stories with new actors and such.

@rvcanuck said:

How will they press the reset button in a way that won't destroy all the dramatic tension they've built up so far?

Well it seems like this will tie in to what Strange saw and why he gave up the stone so easily. All this had to happen for the 1 successful outcome Strange saw. So I think it will end up being a somewhat plot driven, logical "reset"

Calling it now: Avengers 4: Endgame.

From the characters still left they have the brain power to figure out a solution. Its a comic book movie and i'm sure viewers will be expecting main characters to return at some point.