Usually, Marvel's comic book super-mega-crossover events end up plagued with massive delays that screw up the timeline of their corresponding line-wide relaunch events, with books set in the aftermath of Secret Wars or Civil War 2 hitting stores month before those stories conclude. That isn't the case with Inhumans vs. X-Men, or, at least, it isn't the case so far. There's still time for Marvel to screw it up before the X-books are relaunched with ResurrXion. But so far, so good. All three issues of the main book, as well as its tie-in issues in the regular X-titles, have come out on time.
It's the trailer that's late.
Normally, trailers are released ahead of TV shows or movies to build interest in the product. Comic book trailers are different though, and not just because they're often poorly animated and narrated by whatever unpaid intern happens to be hanging around the office when Marvel records. They also, apparently, don't need to come out until three issues of the series they're promoting are already on shelves. Let's be honest here: the purpose of these things isn't to actually sell comics, because the only people likely to watch a comic book trailer on the internet are the people who are already going to read it anyway.
It's with that in mind that Marvel figured, screw it, and released a trailer for Inhumans vs. X-Men, even though Inhumans vs. X-Men #4 is set to hit stores in just two weeks. You can see that trailer below (but haven't you wasted enough time reading this article already?):