Considering that BlackBerry Messenger is PIN based, and has been exclusive to BlackBerry devices only since its inception, I find this "rumor" very hard to swallow. Windows Mobile has had BlackBerry Connect for some time now, and even they don't have a version of BlackBerry Messenger.
However, I am not full of pride, so should I be proven wrong, I will come back to this thread on that very day and say I was wrong, and I will apologize. I don't see that happening though...