In the episode "the time of the doctor" the doctor is given 12 (or 13) more regenerations. Do you think they'll give him/her even more after that to keep the show going?

The power source of The Doctors’s TARDIS is known, but is there any cannon evidence for what powers his/her sonic screwdriver? They’ve shown The Doctor charge the TARDIS on multiple occasions but never the sonic screwdriver. Maybe its because the doctor gets through them too quick?