I don't, and have never had a horse in this race, but as a casual and occasional outside observer, there doesn't seem to be any reason for the 7800XM to exist anymore. Nor has there been for some time, from what I gather.
When/if it finally comes out, there will only be, what, two or three games for it? And it's probably a safe bet that there won't be any more since, as Shawn pointed out, we have the Versa board now. Even those once-exclusive XM games won't need the XM anymore.
At this point the project seems to be about simply trying to recoup, as much as possible, the investments that were made and just being done with it. Which is certainly understandable. But even when/if it's finished and people finally get theirs after so many years, then what? They can play a better version of Donkey Kong that's already going on five years old?
To be clear, I don't mean to dump on the 7800XM project or the people involved with it at all. It was ambitious and would have been an impressive device at the time it was originally planned to have been released, but due to unfortunate circumstances--some of which couldn't have been helped (devastating health problems) and some which could (feature creep)--its time has simply passed.