I think there's enough wiggle room for fans who don't care for that idea to still argue against it if they want, as follows:

1. This is the only time in 47 years of the show that this has been mentioned. It hasn't been referenced before, and if it was fact it realisitically should have been.

2. The Doctor has made weird one-off remarks before which proved not to be true, and which one must attribute to either his confusion or weird sense of humour. He once told Clyde Langer that "a time lord has 507 regenerations". He told Ian Chesterton that "he build the TARDIS". He told Grace Holloway that he was "half-human, on his mother's side".

3. Although the natural implication of the Doctor's remark is that Time Lords can sex-change when they regenerate there are other ways of interpreting it. After all, 21st century humans undergo medical procedures for gender change if they want it; advanced Gallifreyan medicine can presumably do a much more comprehensive job. Regeneration is not neccessary.

But mostly I don't much care unless it is taken so seriously as to affect future casting of the Doctor. The relationships of the Doctor, and how he works in the series, would be seriously compromised with a female lead. I can't see how the format would shift without losing some key essence. I'd approach it with an open mind but I'd not be optomistic.

That said, you might want to search You-tube for an old Comic Relief (charity telethon) event using the keywords Doctor Who, Rowan Atkinson, Comic Relief. It's quite a long two-part comedy sketch from the years when the show was off the air. it features the Doctor, the Master, and the Daleks. It's quite funny, and it includes a brief appearance of a female incarnation of the Doctor. Oh, and it's written by a little-known-at-the-time writer called Stephen Moffat.