The last answer was about six months after launch, but they're not setting anything in stone in case things change or legacy end up retaining a huge advantage over non-legacy at that point. I'd expect an announcement shortly after 2.1, and pure speculation, mid to late March for the transfers to open up. But who knows what data they have and what they're seeing. Could try getting the question into the next Live Letter.
Edited, Dec 2nd 2013 5:55pm by Medieve