Another good point with River Song.
I don't see the Doctor changing more than usual, but I anticipate some new and fresh reactions from other characters, especially enemies of The Doctor, or civilizations that won't listen to a female. Same character, new dynamic. They won't mess with the essence of the character, especially trying to convince audiences for the first time that a female is The Doctor. As usual, it will probably take a few episodes before the character is fully formed, and we've got a new showrunner on top of that, so I'm not going to be too critical right out of the gate. I wasn't sold on Capaldi right away either, but now he's one of my favs. Such is the Doctor Who cycle.