Comment by Analemma_

If they can't stand on their own feet, I imagine somebody would/will buy GitHub at a firesale rather than see it disappear completely. For all their missteps, they have developer mindshare that is the envy of everyone. If we're lucky it would be someone like Google or Microsoft, if we're unlucky it might be Oracle or SalesForce. Whoever it would end up being though, GitHub won't just vanish.