Oh boy, the reason Roblox was this famous was that anyone could share their games publicly and people could play
Having a subscription kills Roblox and its ecosystem.
For context, Roblox has 170 million peak concurrent players, All of Steam had 85 (I got this data from someone at hackernews's comment)
This might be the end of Roblox. I hope more roblox's alternative spring up preferably open-source. There is luanti which is a minecraft alternative but I suppose a lot of games can have overlap to luanti and it runs on lua too.
I think Hytale can grab some marketshare because its modding tools are realy good. And they are built into the game.