The last we heard from Ian Mckellen he said he wasn't going to wait around for The Hobbit. So there was a time that he wasn't really looking to come back and reprise the role that he played so wonderfully in The Lord of the Rings. What a shame that would have been. Here's the quote from that,
I’m not under contract and my time is running out, and I’m enjoying working in the theatre. And frankly, I would like to race after doing Waiting For Godot, get on with doing another play, but we’ll have to see. I don’t give the producers the impression that I’m sitting waiting.
Thankfully, it seems like his attitude has changed, because now in a recent interview it's revealed that the actor is slated to reprise his role as the wizard Gandalf in the upcoming Hobbit films. There's been a lot of talk that the problems over at MGM are starting to clear up, and that there is a chance that the film will start shooting in January of next year, which he also confirmed in the interview saying, "The aim is to start filming in January"
This new found optimism from McKellen shows that there is a good chance that everything we've been hearing is true!