The iTunes credits look like they've had the famous collabs left off on purpose to make it a surprise.
Having said that, I've seen no proof at all that Nicki is on it. Somebody just said it with no evidence and it's been spread.
Edit: I found the French article that mentioned Nicki. My French is not perfect but I think they're referring to his previous work with her, and they go on to talk about Titanium.
http://www.nrj.fr/artistes-509/fiche...lbum-sur-nrj-#