Seems like the guys over at NITDroid have done quite of a nice job at getting JellyBean (Android 4.1) working on N9, like proven by the video below.
Android 4.0.4 (ICS) is still the one available and recommended from NITDroid community. Even so looking at the video it wont probably take too long before you see stable JellyBean release for N9 as well.
Video by drunkdebugger
