We already know that he has a role in the upcoming arc that will play out between Avengers: Infinity War and Avengers 4, and the little teases that we have received seem to suggest that Clint may get a badass new look and an entirely new identity as Ronin at some point — which could explain the hesitance to show him.
One thing worth noting is that Hawkeye’s omission from the Avengers: Infinity War marketing definitely seems intentional.
Whatever the case may be, it is arguably now undeniable that fans want to see more Hawkeye, and they will resort to creating their own art to make that happen if they have to.