Hopefully he will stay that way when someone hands him a few billions.
> Stardew Valley sold over 400,000 copies across Steam and GOG.com in two weeks,[12][64][65] and more than a million within two months. [1]
> By January 2020, Stardew Valley had sold over 10 million copies across all platforms, with that figure rising to 15 million by September 2021.
This makes it way easier to make the choice the second time round to solo-develop an indie game, and be able to take the time to make it just as you want to make it.
The fact that it isn't obvious, makes the choice of making more quality indie games even more laudable to me.
Anyway, you're probably right about the timeline -- I suspect the "mere" millions ConcernedApe made to be about the ceiling for individual game devs, selling the store or no.
Anyone with some business acumen can look at the game, and realize that there's a ton of untapped potential there. Merchandising, licensed show potential, faster release cadence for new games/content, more complicated versions of the games for adults (MMO), less complicated versions for small children.
The merchandising thing seems like a no-brainer. Children really love toys associated with video games, movies, and the like. I wouldn't even think of it as selling out or milking the brand, it is letting people enjoy the game in a way that doesn't involve sitting in front of a screen.