Unless he goes down the whole there was a regen cycle before Hartnell thing which I reeeeeeeaaaaaally don't like the idea of. I dont mind the show tapping into that time period with hints but the mystery of what happened before is such a key part of the show for me. The Moff threatened this with the name stuff, what happened in Listen and when Clara popped up on Gallifrey but he always maintained the mystique. The whole Doctors name thing was basically using the mystery and then shifting that into the War Doctor not being called the Doctor.
I'll explain the 2-3 theory for those that dont know. It basically stems from not seeing the regen and massive a continuity error.
So the 2nd Doctor is put on trial by the Timelords and is basically executed. They force a regen and dump him on Earth where he is exiled and sort of works for the Timelords in a loose way. It looks like this-
(Dont watch this Pedz I know it hurts you)
Most importantly this is when the Timelords FIRST APPEAR and when the show invents them. When the show came back the following year its like this-
However part of the trial has the Doctors companions sent back to their own time with their memories wiped of their time traveling with the Doctor. When 2 comes back in the Five Doctors they even use this to solve a trap where the "ghosts" of his companions appear and remember what they shouldn't. But how does the Doctor remember this if he was immediately regenerated and exiled? Then in the Two Doctors when 2 comes back and meets Sixie things get seriously stuffed. The 2nd Doctor and Jamie are sent by the Timelords to investigate the goings on in a space station. Jamie should have no idea about the Timelords and they shouldn't even know where the Doctor is. Same with the Three Doctors. So the fan theory invented to patch this is that before the exile the Timelords use the 2nd Doctor as an agent of sorts. Its
potentially hinted at in this bit from the 5 Doctors where he says that he is bending the rules being there.
I think the writer, Terrance Dicks, knew it didnt make much sense and put that in like a really early Timey Wimey explaination so that we can have some fun with all the Doctors! But the stuff in the Two Doctors is simply a massive cock up tbh.
Its known as the Season 6B theory-
https://tardis.fandom.com/wiki/Season_6B Where the 2nd Doctor has additional stories set after his trial but before his exile.
Long story short Doctor Ruth could be a version set after "6B" and before 3 takes over. But this dicks over the numbering and the number of regens the Doctor has had which is pretty strawberry floating important for The Time of the Doctor. I find it laughable that this could be the solution to the Ruth Doctor mystery. If people moaned about the Moff using a lot of continuity references (despite him reintroducing anything from the classic run first) then this would be madness on another scale.
If we take Chibbers at face value and assume he isn't lying to protect the stories (totally fair thing to do imo) then I can only assume its a future Doctor (I don't dare think about pre Hartnell
) with memory issues. Which would be cool as I've always wanted a future Doctor story but in my head they basically turned up to save the day having failed to do so with the previous incarnation. Not whatever the heck is going on now.