Linux will be the ultimate test for this. Linus will eventually retire or die. The individual that takes it from there sets the future for all open source. I cannot imagine open source existing if the kernel maintenance is squandered.
There has been open source before Linux and there will be open source after Linux. Yes Linux is a flagship project but the whole culture of open source is much broader than it.
Disagree, Linux is too big to fail. Too many people depend on it. It may get chaotic, but worst-case distributions will start collecting patches, as they already do for many unmaintained projects. Eventually one or two of them will emerge as the new upstream.
Linus should take a lesson from history and appoint the successor in advance, and publicly groom that person for the role, so nobody would have any doubts.