Since 10 used a regeneration to heal himself in Journey's End, having another Doctor who's forgotten makes the limit very much a subject for the special, as it means he's already used his allotted 12... So we may see definite confirmation of that limit being tossed out the window.
(Since it's been previously established that the Timeys could give out new regen cycles, I've always sort of imagined that the limit has something to do with the number of Timeys- Perhaps there's a race-wide number of regens split between them, which at one point was subdivided into 12 each, but now that there's just the one guy left, he can have them all...)
Yes but then River used regeneration energy to heal him in Let's Kill Hitler so who knows what that's done to the limit.
And of course he used some energy to heal her wrist in Manhatten...