Due to over a dozen crossovers over the years, it has been established that xenomorphs and yautja (Predators) exist in the DC Universe, Top Cow Universe, Dark Horse Comics' Comics Greatest World, the world of Magnus Robot Fighter, Judge Dredd's 2000 AD, as well as at least one Terminator timeline. How would you feel if it was established that they lived in the Marvel Universe as well? While making them a standard fixture like the Kree probably would not happen (though it would be awesome0, I think some crossovers might be fun, such as Wolverine fighting a Predator or the Guardians of the Galaxy battling a hive of Aliens. This could be expanded upon if the Engineers were brought in and interacted with several of the other advanced Marvel alien civilizations.