I saw The Dark Knight last Sunday, and absolutely loved it!
But Robin? I think there was one Batman movie that had Robin in it.. I think it was called "Batman & Robin".. and I seem to remember it sucking, really badly, although I don't remember the plot at all (which is probably another good sign that it did, in fact, suck).
Timeline-wise, it wouldn't make sense for the new crop of Batman movies (Batman Begins and The Dark Knight) to contain Robin. But, could he possibly be part of a sequel? He just doesn't seem like a vital character at all, in fact I think (unless there was a REALLY strong plot) that he would actually be detrimental to the story.
Plus, what would his costume look like? We've practically outlawed the spandex costumes used during the era of the Batman TV series – so, what does a sidekick wear these days?