In the media-tv/xbmc-9999.ebuild: The RDEPEND: media-libs/libmpcdec Needs to be replaced with: || ( media-libs/libmpcdec media-libs/libmpcdecsv7)
media-libs/libmpcdec -> Format SV7 support. media-libs/libmpcdecsv7 -> Format SV7 support, libmpcdec renamed. Both are R.I.P., and won't be useful for newly encoded files. New format is SV8. The support for SV8 is in >=media-sound/musepack-tools-444. It has a new ABI and API. If XBMC can't use the new format, the dep. should be simply dropped. I wouldn't waste time on converting it to libmpcdecsv7 renaming.
I mean >=media-sound/musepack-tools-444 has support for both, SV7 and SV8, including tools to convert the old SV7 files to the SV8 one.
Samuli dropped the depend as xbmc uses ffmpeg for SV7/SV8 now