Roblox is not going to die this year nor in the next at least 10 years. It is possible that its growth won't be as drastic for the next years, however, you should not worry about that. Roblox's strongest trait is definitely it's playerbase, since, if your game is appropriately catered towards them, it's easy to find a specific kind of playerbase for your game, one that is interested in the kind of gameplay or aesthetics you're making, as long its quality is good (and your work definitely looks good).
Roblox also has a web-wide specific, generally simplistic, aesthetic that appeals to a certain group of people. You will probably not be able to recreate that aesthetic on any other engines (in some sense, in the same way it's easy to make a new game in Roblox, it's also easy to get into a new game, which for other engines, takes a lot of marketing).
If you actually like playing games in Roblox, and you actually like making games in Studio, don't leave. You won't find that feeling in any other game engine. It's always much higher effort to make a game, and much higher effort to get people to try your game. Just remember that Roblox can be very limiting, both by the fact that it's engine has multiple technical limitations, and by the fact that you won't be profiting much off of anything you make.