>>2495>Linux has always had endless forks, that's how it's developed. Plus it is pretty much unavoidable for vendors that need to put stuff in it that upstream won't take.Only hard forks matter in this case though. μClinux, vendor specific forks, or distro specific patches will never abandon upstream, because it has the momentum in regards to hardware support and testing.
Competitive forks will either consist of a sizeable portion of the former upstream developers and/or need reliable funds proportional to their problem domain (which is substantial for a general-purpose kernel). Even then an unambiguously technically superior fork with experienced developers may stagnate eventually (see lucid/xemas).
Debian+Canonical or Freedesktop+Redhat could maybe pull of a successful hard fork, but they won't want to.