Another thing that would reduce the pain to contribute to GCC is a code base with a lower entry barrier. Despite the introduction of the plugin architecture in GCC, which already lowered it quite a bit, the GCC code base remains held as harder to hack on, less modular, less versatile than the LLVM/Clang code base.
The rate of progress on Clang has been impressive: self-hosting occurred only two years ago, followed three months later by building Boost without defect macros, and six months later by building Qt. On the day g++ 4.7 is released, clang++ is the only compiler whose C++11 support can be said to rival that of g++ (clang++ doesn't support atomics and forward declarations for enums, but fully supports alignment).
GCC isn't alone in not having switched to DVCS yet: LLVM, and its sub-projects, haven't either... However, getting commit access there is quite easy, and no copyright assignment paperwork is required.