It'd be a shame if their two main sources of income (openai and anthropic) were to go bust...
Sure, and they'll be cognizant of that risk when considering expansion. The lessons of the dotcom fiber boom aren't that distant in memory.
I don’t think they will. There is too much money in it now.
They are probably too big to fail already (and too friendly with the current US gov). And even if they fail, open-weight models will take over as the usefulness of the tech behind has been proven.