The fact is, lots of people are very happy using AI tools, and most of those hook straight into GitHub. If AI is driving all this new code, it's only going to make moving away from GitHub more painful.
Businesses I've spoken to hate the idea of moving their code forge. Migrations like that suck and they're expensive. There isn't a meaningful differentiator between the other managed options, so the goal would just be to stand still. Unless GitHub's stability spirals fast I don't see a big wave of businesses leaving.
I say all this as someone who's been moving their code over to their own Forgejo instance. I'm all for more competition and fragmentation in this area, I just don't think it's happening soon.