OSX Xeon clone licensing is not an impossibility.
To be honest, if they went that route just to keep us dedicated tower users happy, I would have no problem with it as long as the licensees put out reliable machines. If that happened I would get one instead of moving to Windows, simply because I'm one of those dedicated tower users.

I remember back in '96 working on a Radius model that was quite cantankerous and would hang up constantly (though that could have just as easily been the OS of the time).
On another note, I have a hypothesis. First, let me say that I believe Apple will release a MP refresh. That being said, I think it's possible that they're trying to generate anticipation/demand around the refresh since (apparently, and according to what I've read) the sales of the current MP haven't been as good overall...? Look at all the threads over this site (and others I'm sure) and you'll notice varying degrees of mania about the whole thing. I think Apple may be trying (among other things I'm sure) to see a sales boost when the refresh comes out. All of those who've been patiently (or not so patiently) waiting seem to long for it, because there's been no news and because the time has drawn out so much.
Generally speaking (and not across the board, as there are exceptions with specific situations where folks have to move on), would any dedicated user really stick with their vehemently expressed threat and/or decision to move to Windows if Apple announced suddenly, after all this time, a MP refresh was being released, say, in a week?
What if Apple sent out an email tomorrow announcing a new MP has begun shipping? Wouldn't all that grief/worry/anger/sorrow/etc. be turned around (and quickly) with the net effect that sales would boom because all those dedicated users who've been waiting for so long finally have what they've been waiting for?
Again, this is generally speaking. Not saying it would be true in the case of all users, but the point is: what if Apple has been either intentionally stalling the release, or using the various technology delay factors to their advantage (and either way the silence) in the attempt to generate anticipation/demand?
Hmmm...