Well, looks like
the rumors were true! While the cameo sounds like a fairly small, light hearted one, it should be interesting to see exactly what role Hugh Jackman's Wolverine plays in the movie and whether there are any hints of him being the one mutant Matthew Vaughn is planning on introducing in the sequel!
UPDATE: Now that the story has been leaked, we know what the scene is, and Hugh definitely IS playing Wolverine. Here's the cameo as described by the guys at Bleeding Cool...
Half way through X-Men: First Class, as Professor X and Magneto are travelling the world looking for mutants, they come across Wolverine, played by Hugh Jackman, in a bar. Before they can get a sentence out, Wolverine, without looking at them tells them to "Go [frick] yourselves." They leave.
The character’s appearance gets a laugh, his attitude and language gets a double laugh, repeating on itself, through the audience. It’s a superb scene, well played, well staged, well placed. And it’s the only moment such language is used in the entire film. We loved it.
X-Men: First Class is set to be released in the UK on June 1st and in the US on June 2nd.