Avengers 4 might be the film that resets the MCU as we know it, but with Infinity War promising sweeping changes as well, it would be wise to expect a change in the Avengers roster once it ends.
With deaths, resignations and new arrivals aplenty, Infinity War is set to be every bit as big a game-changer as the comic it takes its name from. Whether that's a good thing will no doubt depend on how you feel about the MCU, but - as in life - change is natural. Marvel have a massive toybox to play with, and with certain actors due to depart from the franchise in some way, sooner or later, reinvigorating the roster was always bound to happen.
Though the team for Infinity War is admittedly huge, as will be the one that takes to the screens in its sequel, the matter of who'll officially comprise Earth's Mightiest Heroes is a whole different matter altogether. The current team, made up of Iron Man, Black Panther, et al. is but a shadow of its former self, and while friendships will soon be mended, things aren't just going to go back to the way they once were.
They're Earth's Mightiest Heroes, but with a threat like this, they'll never be the same.