I think people (Steven Moffat included) need to realize that when people say they don't want a female doctor, it's not because they hate women, or think female actors in any way inferior to males. Doctor who has, in it's time, had some superb female actors, such as Catherine Tate, the amazing Liz Sladen... and I love them as much as any actor who played the Doctor.
The fact is, The Doctor is a male character. He's always been a male. Young, old, fat, thin... But always male. You start changing genders, you change the fundamental aspect of the character. They just about managed it with the Master, as he's a supporting character at best. The Doctor is the central figure. It's too much of a stretch. It wouldn't be done to take the character on a new journey. It would be done so the BBC could market the show to high heaven. For all the wrong reasons.
Why are people so desperate for this to happen? Are they eager to see Romana return as a man? Susan coming back as the Doctors grandson Simon? No, they are not. Why can we not have a male hero, the finest of them all, and people just be satisfied with that? The whole thing is just silly!
Give us strong male and female companions. Give us as many female characters as you like. But the whole point of regeneration is the Doctor remains the same man. Different in many ways, but fundamentally the same character. To change his gender when its never happened before, it's just too far.
So in answer; I hope it never happens. If it did... I honestly don't know.