True, it's hard to predict. Infact, it's not even hard, I'd venture to say it's probably impossible, considering the difficulties and challenges that they say they're facing.
However, if whatever beta version they have right now is good enough to make a "Demo Preview Vid," it's probably good enough for a public beta? If anything, that'd help their work to de-bug it, as the more people you have testing something, the more results you're going to get.
I'll be honest, I stopped seriously checking the forums every day to see if the release was out in December, and when it comes out, I'll play it and whatnot, but I'm really dissapointed that the MTA team couldn't listen to the requests from it's dedicated remaining fanbase.
.. Rob out.