I love Ridley Scott, but he's nothing if not a careerist. Right now he's got 18 titles "in development", according to IMDB. He's like Quentin Tarantino in that he talks up a lot of possible movies, but he actually works on them. So he's like an older Steven Soderbergh (even if he doesn't do quite as much stuff as Soderbergh) - two years between movies is a long time for him, and he's a pretty old dude. His record lately has been spotty, but which legendary Western director doesn't have a spotty record in recent years? Even Altman was putting out middling stuff in his twilight.
That having been said, his two swings at sci-fi are truly genre-defining. I think it's suited to him - a lot of directors apparently sour on spacebound sci-fi after their first crack at it (the only concrete example I can think of is Danny Boyle, but I'm sure there are others).
Anyway, /FILM has some extra info - one, that Scott has actually planned out two prequels, although he's only working on the first at the moment, and both movies will be in 3D. Yay?