Speaking with io9, the producer said: “I think for a film series that is going on 10 years and is gearing towards a conclusion with Avengers 4, which you don’t usually have in these kind of movies, you can sort of do the math.
“And realise it’s the original Avengers that are left.”
It really is rather fitting for the Avengers, who are presumably bowing out (alive or dead) after Avengers 4, to have to work out how to save the others.
Essentially it’s up to original team to save the MCU, the future of the franchise is literally in their hands. And no doubt will involve self-sacrifice.
As for Hawkeye, the only original member who didn’t appear in Avengers Infinity War, we know he survived the Snap thanks to some leaked concept art.
Avengers 4 is released in UK cinemas on April 26, 2019.