I doubt it. Unless the GNU team decided to add it, I don't think there's much incentive. Are there targets out there that gcc supports which aren't supported by LLVM? Probably not too many. Commercially, LLVM is much more attractive than GCC, so semiconductor companies which make CPUs/uCs/DSPs/GPUs/FPGAs/etc are probably more likely to create an LLVM backend than a gcc one.