Have a look:
Ullmark is not currently signed for the 2020-21 season and is scheduled to become a restricted free agent unless the Sabres sign him before then.
This seems to make it very clear that Ullmark will re-sign and return as the team’s number one goaltender. His backup, though, is still up in the air. Even though Carter Hutton is signed for one more season, we’ll see if the Sabres are content with him after his inconsistent play last season.