It's actually the opposite; GCC is being ported to C++ because there is actually so much interest in continuing to hack on it. The current codebase is being hobbled in various ways by being limited to pure C. GCC even has a (nasty) internal garbage collector, despite being a C program: http://gcc.gnu.org/wiki/Memory_management

If GCC was dying as you said, nobody would be interested in such large refactors that have no point other than to make development easier.