Hi,
No news yet, there are many theories, but that's not what you're asking for :-D My suggestion, based on many issues the MM update is causing folks, is that once its released, and you do download it, be prepared for issues to occur, as with most updates, it happens. Now, with that said, there are many who never complain or have issue after these updates.
Moving on....just be patient, as the delay probably means, they're working out all the bugs that the other early releasing carriers are having! :-D
Chris