Whatever our predictions are for the next movie will be wrong.
But my prediction will be that Black Widow takes the big leap of death. Hulk finally comes out, but it's not just Hulk, It is WORLD BREAKER HULK!!! Or even better HEART OF THE MONSTER HULK will absolutely crush Thanos. Now Thanos with the Infinity Gauntlet is still a different story. Thanos with the gauntlet controls the fundamentally forces of the universe. So no one is going to over power Thanos. Thanos without the gauntlet will get completely pummeled by World Breaker Hulk.
So Thanos will lose the gauntlet by cunning not force.