The BBC has announced that Steven Moffat will replace Russell T. Davies as "Doctor Who" showrunner for the new series' fifth (not fourth, as I originally wrote) season, which won't air until 2010. (I believe David Tennant has some kind of theater gig that will sideline him for a while; there are four movies planned to air in 2009.) Thoughts after the jump...
I'm very glad to hear this, especially as there had been rumors that the BBC considered Davies so integral to the success of the new series that they planned to discontinue it (or just produce occasional movies and specials) whenever Davies decided to leave. Obviously, Davies deserves the lion's share of credit for how well the show has been reimagined while maintaining the elements the fanboys loved. But Moffat's episodes have consistently been the highlight of each season of the new series, whether it was season one's London Blitz two-parter "The Empty Child"/"The Doctor Dances" with the gasmask people (pictured above), season two's "The Girl in the Fireplace" with The Doctor romancing Madame De Pompadour, or last year's frightfest "Blink."
My only concern is whether Moffat can pull it off on a regular basis. It's one thing to parachute in for one or two episodes a season (I can't wait for his two-parter later this year) and another to have to run the series. Obviously, Moffat has showrunning experience before (notably with "Coupling"), but it'll be interesting to see how (or if) he plots out those season-long arcs Davies seemed to love.
Also, this increases the possibility that, whenever Tennant decides to go, we might get James Nesbitt from Moffat's "Jekyll" as the next Doctor, which would be awesome.