I've believe I've read mid-January, though I can't find that source again. I'm quite excited for it, though I probably won't be buying one due to finances and already having a fantastic laptop. I'd love to have a pressure sensitive, capacitive tablet that has some power and a lot of portability. It sounds like it will have a lot of what I have now in my laptop, but smaller.
Heck, I might even be willing to sell my current laptop, then buy one (if it's reviewed well) and build a desktop.
Lenovo W520 w/Windows 8.1
IBM dx340 (Hyper-V 2012, Windows Server 2012, OpenSUSE 12.3)
Nokia Lumia 928