Sounds like you think hes a great prospect, which is fair. I just don't see him as the "Bruins main guy in three years" yet. We shall see though.
I think he could be, but he could also be a place holder for someone else in the pipeline.
Rask will be be up in 3 years and at 34yr old who knows what his role will be. Maybe he's still a #1, maybe he's nose dives and is a back-up, maybe he retires.
Zane could very well not even be with Boston in 3 years. His AHL numbers are nothing great and he's been lit up at the NHL level.
Keyser could be a guy that competes again Vladar. Kyle should have around 2 years of pro hockey experience (maybe splitting time with Vladar in the AHL) and he'll be around 22yr old.
Swayman in 3 years (assuming he doesn't leave early) would be finishing his senior year a Maine. Barring some insane development (which if it happened I doubt he stays at Maine 3 years) he's not going to jump straight to the NHL.
So assuming Rask doesn't stay in Boston after his contract is up and Zane is axed to make room for Keyser, its possible that Vladar could be your #1 goalie going into the 2021-2022 season. By the 21-22 season, Vladar will have had 4+ years of pro experience is would probably be the most NHL ready of the goalie Boston current has in the pipeline.