[Batty]

Or... okay then. xDD

According to the 'rules' set out by the old writers, a Time Lord can regenerate 12 times, meaning a total of 13 different forms.
However, in the current state of things, the old writers didn't expect the Time Lord homeworld to be destroyed, so what they thought seems to be irrelevant.

Now, since the Doctor is the only Time Lord left, he has complete autonomy on the Eye of Harmony, whose only remaining link is deep in the Catacombs of the TARDIS. It is the Eye that gives a Time Lord the ability to regenerate and so if no-one else is governing it, it's up to the Doctor how long he lives.

So as long as the time lord council isn't about, we can have as many seasons of Doctor Who as the writers and producers want. YES! LONG LIVE DOCTOR WHO.