The main thing about a movie for me is that it doesn't have to be the current Doctor in the role. After all, any story is a stand alone, and not part of the series as such. The film can postion itself into any time line it chooses. The McGann/Eccleston changeover could be one theme used. But with so many alternate histories out there through the books and audio series, anything is feasable.
Go on, Doctor Who-Shada the Movie.
And it would be a nice "pension" for any actor who fancied another crack at the role, whilst the series continues with it's Doctor.... and then in 27 years when David Tennant gives up the tv role, he can make a film every year, having taken over from Eccleston or McGann (or Peter Davison, who one day soon is going to morph into William Hartnell).
Just a thought.