the doctor that isn't our doctor but the next doctor
The শিরোনাম of the special is called "The পরবর্তি doctor"
But I don't think it means the doctor will regenarate
আপনি see in RTS's book it says that the doctor meats the doctor (I think that means future doctor) and then becomes his companion thats why it's called the পরবর্তি doctor, even though the doctor doesn't regenerate we see what the পরবর্তি doctor will look like
So to মোড়ানো it up the শিরোনাম "The পরবর্তি Doctor" doesn't mean that the doctor will regenerate it means that we see what the doctor will look like after hi regeneration which will be in a future episode
As if regular cybermen were bad now the doctor has to deal with cybershades