So with the casting of the Twelfth Doctor now over and done with, Ive seen many complaints about the fact no females or persons of colour were considered. In terms of POC I would love to see that in the near future, but Im personally not so sure about a female Doctor happening anytime soon. I completely understand the want, nay the need, for a female icon in pop culture, especially sci-fi, but just because Doctor Who is a show which would allow the change of gender of its main character should it bow to the political correctness? Moffat has received heat for not even considering auditioning a POC or female, so I do have to point out that Russell T Davies did the same thing for both of his castings of the Doctor. Christopher Eccleston (the Ninth Doctor) was on a short-list that RTD had written and nobody but David Tennant was asked to audition for the Tenth Doctor. Moffat is the only person that we know actually did audition a number of people of the role, and though we dont know who those people were, it is completely within his right to only audition one person he believes to be a fitting replacement. Not only that, Moffat asked friend and fellow Who writer Mark Gatiss to write down a list of potential Doctors to follow Matt, at the top of which sat Capaldi's name. But anyway, back to the female Doctor discussion. There are differences between Time Lords and Time Ladies which should be noted as well, specifically the control of the regeneration. When Romana regenerates shes able to control her regeneration much better than the Doctor, and in fact changes her looks several times over in specific ways before settling on a specific look. Mels, when regenerating into River Songs form, makes comment on focusing on a dress size and later that she may bring her age down gradually (a joke for us due to Kingston playing the character in reverse order and thus looking older at Song's last/first appearance). One could argue that Romana could only alter her looks because the Time Lords were still around, but the Doctor never had control over his regeneration at any time. He was always surprised by how he turned out. So it seems more than likely that this control is an exclusively female ability. There are probably three main contributors to the belief that there could be a female Doctor. The biggest and most recent is of course the case of the Corsair. It was mentioned in the Doctors Wife that the Corsair changed genders several times before she (or should I say he?) died. But one thing is for certain - although we know the Corsair changed genders, we do not know the circumstances. There have, however canon you consider them, been female Doctors though. The most commonly known one is played by Joanna Lumley in the Comic Relief special The Curse of Fatal Death, the Thirteenth Doctor.
But there was also another, in a Doctor Who Unbound story titled Exile, in which the Doctor regenerated into a female in order to hide from the Time Lords. The gender-crossing regeneration into a female was caused by committing suicide. It was outright stated that to change gender the regeneration must be caused by suicide. I also believe this could why Eleven originally thought that he was a female (this is also the second reason people believe he could change genders) as mentally Ten committed suicide (though really a sacrifice) in order to save Wilf. The third reason people believe the Doctor could be a female is Nine's line in The Parting Of The Ways stating that he "could be anything". Whilst a lot of people have taken it literally to meaning he could be blue, or have square feet, or even no head as Nine mentions, I believe it wasn't quite as literal as that. I believe it was more of an "oh I'll have anything for dinner tonight" statement. When you say that it doesn't mean you're happy to have a train wheel for dinner. Personally, if there were to be a female Doctor, I would want it to fit in to the Doctors life naturally. Since we dont know the context of the Corsairs gender-changing regenerations, we cannot say that it is simply a natural thing that can happen randomly - and indeed if it is that does not explain eleven (now twelve) male bodies in a row. Is a female Doctor possible? Hell yes. Should it happen at some point? Of course! But should Moffat have considered it with the Doctor we have? Not at all. Suicide would be the most depressing end for Eleven. And Moffat is evil when it comes to hurting the fans emotionally but I dont think he is pure evil. Either way, whatever happens in the future, Im sure Capaldi will be a fantastic father to Jenny if she comes back. Or shell be a mother, possibly? Possibly a grandmother too! Or would it be grandfather? Who knows?