If the eggs are simply manufactured to destroy earth at the end of the film, meaning the Xenomorphs did not exist until 30 years prior to Alien; not only would it destroy the canon compatibility of the AVP films (some do care about them), games, and many of the comics, but it might also conflict with the idea of Alien Queens in general. On another note, It'll be difficult for me to watch Alien and hear Dallas mention "Seems fossilized, looks like it's been dead a long time" when this takes place only 30 years before Alien. All this recent footage is quite worrying, not to mention Ridley hasn't exactly been at the top of his film making game for a while now.