Oh boy... not this again...
We only have one minute or so of footage, but. Everything points to this being a new game.
In that minute or so footage, we see all new areas and Pokemon from even Sword/Shield. The only thing that it could be other than a sequel is a straight up reboot, which would still make it a whole new game. And since a general timeline for Pokemon Snap would be completely unnecessary, I cannot fathom why they would do that.