As more information comes out and more theories surface, it has become clear that John Hurt's Doctor as revealed in the last episode, creates a deep mystery of who the Doctor really is. We have watched in the surety that we have seen all the incarnations, starting with the First Doctor who ran away from Gallifrey with his granddaughter (whose fate has never been revealed) up through the Eleventh Doctor who found himself facing his own grave on Trenzalore. We are given this partly because we have seen each incarnation morph before our eyes. Or have we? There is one break in the middle. We have not seen the regeneration of the Eighth Doctor into the Ninth.
That makes three different periods in our favorite Timelord's life where John Hurt could fit; he could be a later incarnation, between the Eighth and Ninth, or before the first. I am hoping for earlier, but in any case, if John Hurt's Doctor turns out to be another incarnation, it means that when we see the regeneration at the end of the Christmas Special, this is the last Doctor.
Or is it? I love to put on the old episodes and I am currently running through at least one story from each season and the first and last episode of each incarnation. There are some fun facts to be found, especially when you do some searches and find out the mind of the story writers and producers who created the stories. What I've found is that during the eras of the Fourth and Seventh Doctors, there were some ideas afoot. In The Brain of Morbius, Morbius and the Doctor engage in a mental wrestling match and the Doctor loses. We see all of his former selves and some others. While most people today think this is Morbius, it is indeed the Doctor and the writers and producers intended it to be the Doctor. The faces are those of several of the production staff at the time. Then a few episodes later in The Deadly Assassin, we are given the limit of twelve regenerations causing the idea of many previous Doctors to be lost. Then in the era of the Seventh Doctor, there was a substory being built to restore much of the mystery to the Doctor. He was more than he seemed and it was implied, but never stated, that he wasn't just a Timelord. Rumor has it that he was the third member of a trio of Timelords who founded Gallifrey, the others being Rassilon and Omega. And as was established in the 20th Anniversary Special, The Five Doctors, Rassilon was immortal (which makes his return during the Time War make sense).
So is the Doctor limited to 13 incarnations (which the 12 regeneration limit gives him)? We will have to wait and see. One hope is that John Hurt is not playing a new incarnation, but one of the previous ones. The most likely is an older Eighth Doctor or a younger First Doctor. I think a younger first Doctor makes more sense, especially considering some rumors about the 50th Anniversary Special and that inserting another incarnation will cut the show shorter or force them to deal with the question of the number of regenerations the Doctor ends up with. It would be an interesting question to find out why the Doctor ran away from Gallifrey. What did he do, who was he before. It can be answered in several ways that does not ruin the mystery of our favorite Timelord.
I've been happy with Steven Moffat's writing so far, so I have high hopes for the special and subsequent Christmas special and the introduction to a new Doctor. The story of the Doctor has been in many hands and it has changed a bit over the years. When dealing with the story of a time traveler who does so much, we can surmise he might have even changed his own past a few times, but it has been oddly consistent in certain aspects. A man on the run from his own people in a rackety old Tardis. As Clara said, "Run, you clever boy, Run!"