They co-wrote V for Vendetta and the last thing they directed was the Matrix trilogy. Although different, these shared a dark tone that I don't think will lend itself to Speed Racer. Of course they can always go in a completely different direction from the original animated series, but then what would be the point of calling it Speed Racer?
Although I'm usually firmly in the "anti-remake" camp, if done right this could be a pretty cool movie. To really work and to retain the feeling of the original animated series it should probably have kind of a James Bond vibe to it IMHO. It should be bright and open as far as cinematography goes, and so far they haven't really done a movie with that sort of look.
Of course the original series is one best left in my childhood memories... one of those things that I have fond memories of, but if I saw it now I would cringe. I actually caught a few minutes of it on Boomerang (I think that was the channel) and I couldn't believe how awful it seemed. That's why I think this movie could work as a remake or re-imagining of the original show. My favorite thing about the show was of course, the car: The Mach 5 was as cool as (if not cooler than) the Batmobile from the 60's show.
Of course in this day and age I don't know if a cool car is enough to carry a movie... then again there is talk of a Knight Rider flick. :-)