We don’t know what Hawkeye’s role will be in Avengers 4, but there are some theories.
In his Instagram post from the set of Avengers 4, Jeremy Renner includes the hashtag #letsstretchbitches, clearly following the Zombieland rule #18 to limber up.
We do know that the characters that didn’t have as much (or anything) to do in Infinity War will play larger roles in this next film.
So this won’t be a Luke Skywalker in Star Wars: The Force Awakens-type situation.