I just remembered something. In "Trial of a Time Lord" (Tom Baker) Wasn't part of The Doctor's sentence to forfit some of his regenerations? If so, he's not going to get the usual 12.
P.S. Yes, the Time lords can do that. If you remember, the way the Tom Pertwee character was created was that the Time Lords forced The Doctor to regenerate, basically forfitting 1 regeneration.