I gather they'll jump straight to Foundation And Empire and Second Foundation, since the first "book" is really a collection of related short stories, with no overlapping characters. Indeed, I'm not sure how you make a movie or two out of this - it works in one medium, but doesn't seem like it would translate well to film (although Kapur seems like the right guy to do it, based on Elizabeth).
I also don't know how a cinematic treatment of the Foundation series could translate well to the big screen.
I would almost perfer a TV mini-series approach for this type of material, but I think it would dilute the interesting aspects of the material for the casual viewer.
I think a movie would likely start the story with Prelude to Foundation which, while written much later, has more of a one-story narrative throughout that would best lend itself to movie adaptation.
I agree with Patrick that a TV miniseries version would probably work best to tell the whole story of all the Foundation novels. On HBO or something, it could work well in kind of an anthology mode that allowed for the shifts in time and characters necessary to the tales (broadcast networks would never allow a program that didn't have one star running throughout). I think the whole project is probably too massive and far-reaching to ever be worked out for film or television, though.
I'd personally rather see a film adaptation of The Caves of Steel or something else more manageable. But it looks like Alex Proyas's I, Robot is pretty much cannibalizing plot elements from that one, so here's hoping it's a decent film, because it's all the Asimov we're likely to get anytime soon.
I've always been skeptical that you could turn Foundation into a decent movie (despite the fact that they are doing so). But Caves of Steel and it's other Lije Bailey sequels - they could be translated most excellently. And I agree that Prelude to Foundation would work much better with its straightforward narrative story.