I think it unlikely that there will be a successful female formula one driver in the near future for several reasons.
The first has been alluded to by Amanda. There simply aren't enough women becoming interested in racing at the lower levels. So even if women and men were completely equal in their innate abilities, you'd still only rarely see women at the top level. Think of it this way, the vast majority of men who get to F3, never get to F1. Then, when you only have the occasional women driver in F3, just by random selection you wouldn't expect them to get to F1 except extremely rarely.
Secondly, again even if the innate ability between men and women was similar, there are social reasons why top level motorsport is an unfriendly place for women. There appears to be an expectation that female motor racing drivers be physically attractive. Robert Kubica may have a nose that you could use as a beehive, and Michael Schumacher had an aerodynamic chin. But if a woman was similarly unattractive, the fans just wouldn't accept it. Just look further up this thread where people say that wouldn't it be great if there was a "pit babe" driving a car. What if a new super-duper woman racing driver resembled a Russian weightlifter? The amount of negative reaction would be huge, and the potential for this to happen will definitely be a big negative discouraging women. Can you imagine the ignorance that such a driver would have to put up with. I've actually seen posts in a forum saying that a woman F1 driver would have difficulties because what would she do when she was unable to drive during her period. And similarly ignorant statements from Bernie Ecclestone drive home that such ignorance and sexism go to the very top of the sport. Not an inviting environment.
(I want to point out here that I quite often find the "Russian weight lifter" type attractive, but realise that the typical male motorsports fan is more interested in the plastic-titted pit babe type).
Probably the most successful woman racing driver ever was Michelle Mouton, finishing second in the 1982 WRC, winning several rallys, and perhaps only losing the championship due the unreliability of her car. And I don't believe that rally driving is that much less physically demanding that F1 driving. Perhaps lower G-forces.
But if we look at the successful women motor racing drivers, they're typically attractive. Look at sultry Michelle Mouton in her prime.

And Danica Patrick appears in men's magazines in her knickers.

So Danica is (presumably) happy to play along with the expected role of female drivers being "babes", and has the physical attributes to do it.
But both of these drivers, if they gained the muscle necessary for F1, e.g. the famed "huge necks", would this still be accepted by the fans and F1 in general?
So, you have the expectation that the women motor race driver drives well enough for F1, but also an expectation that she will be physically attractive. This cuts down the field so much that we're probably only likely to see a female F1 driver every few decades or so.
I believe that it would take a massive change in the attitudes of the majority of F1, and motorsport, fans in general for motor racing to be a sufficiently inviting environment for sufficient numbers of women to participate such that women bubble up "to the top" on merit.