As long as there are people who care about freedom, people will maintain GCC. Even if the worst case happens, and there is extreme fragmentation of proprietary patch-sets to LLVM, we can always still use GCC, or even still use the free parts of LLVM/clang.
While there is some issue with fragmentation of the developer community, I see this as a non-issue. These things generally work themselves out through the natural ebb and flow of chaotic systems (just like the economy is largely self-regulating).
We can always still use GCC. I don't really see where the issue is, am I missing something?