Cross-compilation is irrelevant because Xcode's build system could easily be adapted to use the Intel compiler for i386 targets and gcc for PowerPC targets, and finally calling lipo to create the final multi-architecture (not to say fat -- it's so 90's) mach image.

As for Objective-C, I don't think that would take Intel too much time to implement. After all, a lot of Objective-C's magic is in the runtime (all pure C), not the compilation process.