I'm just curious the 12th (13th) Doctor regeneration was explained. Does anyone have their own theory on how the अगला regeneration will be explained?

The explanation was दिया in the most हाल का special episode, called The दिन Of The Doctor (I think. All of these "...of the Doctor" titles can get me muddled). He had run out of regenerations and was dying. Clara spoke through a slit in time and अंतरिक्ष to Gallifrey asking the other timelords to help him. They sent him spare regenerations. Most प्रशंसकों are assuming he's got another full set now.