I have never worried about D&D failing.
Option 1: D&D keeps doing well, and there continues to be a steady stream of D&D things for me to spend money on.
Option 2: D&D fails, and I suddenly have more money.
Pathologically optimistic me just isn't seeing a problem here. Both options are great!
The only issue that matters to most of is is finding good groups to play with. If we have a good source for that, whatever happens to the company, the brand, or future products doesn’t matter too much.