I wouldn't be too surprised if the details from all of this get pulled into MAME/MESS. It will take some rewriting though as I believe BSNES is written using a number of C++ features (I seem to recall it even needing some C++11 stuff from when I last played with the source). The CPU cores themselves I'd imagine would be fairly easy to port over but I'm not sure how tied in everything is for timing and everything else in there.