That would be funny, going from 12th Doctor back to 8th Doctor with Series 11, and eventually getting back to the 13th Doctor (or if the BBC thinks that is unlucky, have the 13th Doctor come and go within one episode, or the passage from one series to the next, the end of one season being the regeneration and the start of the next season also being a regeneration).



Honestly, the TARDIS was probably there because it was apparently an ancient, obsolete TARDIS even at the time (based on things that have been said over the entire series), and fragment Clara just pointed it out to The Doctor, she didn't put it there.