> What happens if/when Stadia goes under? Who knows, but there's a decent chance of, "tough shit, all your games are gone."

This had now been answered [1]:

> We will be refunding all Stadia hardware purchases made through the Google Store, and all game and add-on content purchases made through the Stadia Store.

1. https://www.ign.com/articles/google-is-shutting-down-stadia-...