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None other than #12
Ohila: 'And here he is at last. The man to end it all. My sisters, the Doctor has returned to Karn. We have always known in our bones that one day he would return here. Such a pity he's dead.' -From 'The Night Of The Doctor'
Ohila, from the Sisterhood of Karn, is referring to the 8th Doctor who was temporarily restored to life by the Sisterhood. Less than 3 minutes later, when he drinks an elixir (given to him by Ohila) he is changed into a 'warrior'. Onset of this change is marked by regeneration energy which begins to flow from the Doctor's body. While his outward appearance is altered we do not witness a full regeneration. Why? Because only the living regenerate... what we witnessed was rebirth from death, not regeneration of life.
In 'The Angels Take Manhattan' we see regeneration energy used by the Doctor to heal River Song's wrist. Full regeneration does not always follow manifestation of regeneration energy.
The body that grew from the 10th Doctor's severed hand, recovered by Captain Jack Harkness, did not have 2 hearts, a key physical characteristic separating Time Lords from humans. The 'human' Doctor is not a Time Lord. His physical form is not a new incarnation of the Time Lord we know as the Doctor but rather a human 'copy' and it is for this reason alone that there has been but one 10th Doctor.
We have no reason to believe that the most recent incarnation of the Doctor is anyone but the 12th.
As a side note, the 'human' Doctor which grew from the 10th Doctor's hand would not have been present in 'The Day Of The Doctor' when the Doctor's other incarnations saved Gallifrey as he remained in a parallel universe with Rose Tyler in 'Journey's End'... moreover, he did not possess a TARDIS.
2 close-up stills:
Note how this close-up shot differs from the other above the cheekbones and below the chin.