It's entirely possible that the 12 generation limit was imposd by the timelords. No Timelords, not limit.
If it's biological, I can see them coming up with any number of means to get around it. From the Eye of Harmony to having one of his clones return and merge with a dying doctor and trip off another cycle.
It's less a question of limits, and more a question of if and how they want to end the series.
If it's biological, I can see them coming up with any number of means to get around it. From the Eye of Harmony to having one of his clones return and merge with a dying doctor and trip off another cycle.
It's less a question of limits, and more a question of if and how they want to end the series.