I for one am not surprised at all that Hugh had top billing for this film. He, along with Halle Berry received those positions for X3 and I believe Ian and Patrick rounded out the top four. I don't believe that Halle has as big of a role in this film (I personally believe that Storm will lose her life at some point in the storyline) so I wouldn't expect her to be in in the top 5. But that being said, I also don't see James McAvoy or Michael Fassbender being billed before their film counterparts--it makes more sense that Patrick would be listed first, then James, then Ian, then Michael, etc.
I agree. Also, it's interesting to note that the "And" honor is not listed in the final scrolling credits. The actor(s) is moved upward into the overall listing towards the top rung of billing. For example, Anna Paquin was listed with her castmates in the final billing for both X-Men and X2--but not last. The link below explains my point:
http://www.imdb.com/title/tt0290334/?ref_=fn_tt_tt_13
http://www.imdb.com/title/tt0120903/?ref_=fn_tt_tt_1
Patrick Stewart recieved the "And" distinction for X3, but the final billing does rank him with the other actors:
http://www.imdb.com/title/tt0376994/?ref_=fn_tt_tt_4
Expect the same to happen with this film. We won't know the exact billing order for these actors until the scrolling credits arrive for this film--the trailer released this week is not a real indication of anything.