During an interview in promotion of Les Miserables, The Wolverine star Hugh Jackman has confirmed long-standing rumors that another member of Marvel's Merry Mutants will appear in his upcoming solo outing.
"Okay, the movie takes place after X-Men: The Last Stand," Jackman told Parade. "My character is at his lowest. He is supposed to be able to heal himself, but he may encounter someone who has worked out a way to really hurt him. And there is a cameo from one of the past X-Men in it."
While it might seem most obvious to have Charles Xavier appear in the film (since Sir Patrick Stewart was one of the first to acknowledge his involvement and he could serve in an advisory capacity if Logan is really down and out), there have been persistent rumors that Jean Grey (played by Famke Janssen) would make an appearance in the film, which would also gel with the report and would make sense if her death is (as one would assume) part of what's got him down.
The movie will presumably lead into X-Men: Days of Future Past, the upcoming X-Men: First Class sequel in which director Bryan Singer confirmed Jackman's involvement earlier this week. That story features Wolverine in a time-traveling story that saw as its "present day" status quo a world in which Madelyne Pryor (short version: a clone of Jean Grey) was on the team, which might open a door for Janssen to return in that film, as well, if that's the filmmakers' inclination.