Chris Lattner, who is Apple's chief architect of their compiler group and also the lead developer of LLVM and Clang, came out to say that whatever Apple pushes to their GCC branch on the Free Software Foundation's servers they should be able to pull upstream, but not code that's found within the open-source GCC hosted by Apple on OpenDarwin or anywhere else. Or GCC code that's found within LLVM-GCC.
After another developer called for Apple to push a fresh source-code tar-ball to the Free Software Foundation server (thereby acknowledging the FSF copyright assignment) so they could pull in all of the Objective-C 2.0 support, Chris Lattner came back to say: "Apple does not have an internal process to assign code to the FSF anymore. I would focus on the code that is already assigned to the FSF."
The belief is that Apple is no longer contributing back as they object to the GNU GPLv3 license. So unfortunately unless things change it doesn't look like Apple's Objective-C 2.0 support will land in upstream GCC. It may come once LLVM's Clang can sit in front of GCC as a plug-in front-end, but until then you're stuck using Apple's GCC or the Low-Level Virtual Machine.