The casting call did state that it was for Avengers: Infinity War, but since production had just wrapped when the casting call went out, it seems likely that this is for Avengers 4.
Both Infinity War and Avengers 4 were once slated to be shot simultaneously, although that plans was ultimately scrapped.
Regardless, the Atlanta Filming account didn’t shed any light on specific details of the shoot but hopefully we’ll have some photos from the set once Avengers 4 filming begins.
It isn’t known when filming will actually taking place, but director Joe Russo confirmed at Comic-Con that production is starting on Avengers 4 in the next few weeks.