It's a sequel. It was always going to be a sequel. It's not like they can really do anything which would make you go, "Oh, that means X, Y, Z never happened," because the other two films had almost completely unrelated events, anyway. The second creatures even looked completely different and had natural vision which looked different, although the fan base has come up with a variety of possible explanations for those. Unless they give the things four arms or something, it's doubtful they'll contradict anything in particular.