Yes, it's already the highest grossing X-Men film ever here and the movie is still on pace to outgross X-Men The Last Stand in tickets sold (it should be there same time next week).
So yes it's not some kind of artificial growth. This time it's not 3D premiums or inflation or Imax or whatever but the actual attendance of the franchise growing. Which is really encouraging indeed.
And given that is not an isolated example, even in the US you may find the numbers a bit dissapointing but there's no deniying that they are showing a significant increase from the last 3 films in the franchise which is encouraging as well (and the reported budget is not outrageous either), I think it really puts Apocalypse on the right track.
Depending on how the next film will turn out, I think the studio would have solid foundations to hope for its first 1B X-Men film.