But I don't think it means the doctor will regenarate
anda 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 selanjutnya doctor, even though the doctor doesn't regenerate we see what the selanjutnya doctor will look like
So to membungkus, bungkus it up the judul "The selanjutnya 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