Dr Who is now immortal?

Odd one this. As every genned up Dr Who fan knows, the Dr and other Time Lords have 12 regeneration cycles before they kark it forever. It now appears that this has been quietly done away with according to the Sarah Jane Adventures in an episode featuring the Doctor.
When asked how many times he can regenerate he replies that "There's no limit".
Hmmmm. It was an interesting premise, with Matt Smith as the 11th Doctor, and the character being so close to the final regeneration. Of course the BBC weren't going to let him die after his 12th incarnation, but I would have thought a bit more effort and smarter writing would have gone into the explanation for his being able to surpass the 12th regeneration.
Lazy writing and a distinct whiff of Deus Ex Machina about it, but I'll keep watching, regardless, as I really enjoy the series as a whole, classic and new. Just a bit disappointing that such a milestone and looming death sentence has been swept under the carpet in such a nonchalant manner.
Of course that now makes him immortal and leaves the BBC free to put as many actors into the role as often as they like, as unlikely as that will be however.