I believe all the movies are cannon. heres the way I see it. The pyramid was destroyed so no need for young predators to come to Earth. Secondly hunting parties could not come to earth without risk of exposure by the human population. The predators knew that their time as a hunters on Earth was over. Its like japanese honeybee, when a giant japanese wasp comes to the honeybees' hive to scout for a killing party. They the honeybees gang up and kill the scout before it can escape and tell the others. The humans one earth would kill the predators when they landed again. So any information they Yutani corporation would have would be from previous. Thus the predators legend would be buried by time. And any mention of the xenos with it. remember the predalien happened within days of the weyland incident. Its possible whatever was told to the weyland crew on the boat from the only survivor was buried soon after the crash in colorado. Yutuni decided that the pred/alien problem was something the humans werent ready for. She probably got her info on the preds directly from the survivor herself. Plus any war with the predators would mean they the predators could unleash the aliens onto the Earth to simply wipe the human population out. Not honorable but a simple solution to a thorny species without knowledge of the aliens. Thus the secret of intelligent life was buried for good measure. So when WY would have come upon the signal all they would have known it as an alien signal. The humans at the highest level would know that they werent alone but with a signal it would mean that perhaps there are more aliens then just the predators who are advanced. Perhaps language experts could see that the signal was related to the preds but not the same. Which they could conclude was another alien species. Which to the humans was the enemy of my enemy kind of deal. What they didnt know was that the ship had the xenos and the space jockeys probably worked with the preds as an independant. but with a xeno, the tide of war could be turned. The previous information from the twentieth century would have told the execs at WY the versatility of an intelligent bioweapon. They could use it against the predators if they ever find their homeworld and are at war or use it against human enemies. Greed takes over instead of survival of the human race. Thus, as they the company expands and uses the xenos for bioweapons. They also find the aliens whether or preds or spacejockeys are releasing the xenos to torment the human race due to the fact that they the humans are meddlesome and greedy. Perhaps the space jockey was originally delivering the eggs to another area that was different so the hunting parties could have different areas to hunt. Perhaps each clan has it own hunting planet or planets and the space jockeys are contracted to keep the planets stocked with viable prey in which to hunt. The planet Earth belonged to one clan that ruled for centuries until they realized their training ground on earth wasnt feasible any longer. Imagine the predator clans like a bigger badass form of the mafia.