No idea. The only people that do (MS/Nokia), don't appear to want to tell us. A good 90% of all WP users haven't had it released, or had some form of release date given.
Why do people keep asking this question? When its out it is out. Its all done by your network carrier. Microsoft officially gave it the thumbs up to be rolled out. So now the network is either testing it or rolling out. If you cant wait then do the DP 8.1