A:CM was an example of a bad retcon, but I wouldn't penalize Blomkamp for that.
But look at who approved it, Fox. Granted we dont know how much they knew abut the story but it was still something they approved, they seemed a lot better about it with isolation, the newest set of novels and fire and stone wasnt too bad. But i would rather them just "play it safe" and do something new and leave the originals alone
ANd by play it saf ei mean dont screw up whats already on rocky ground. Fans cant agree on alien 3 half the time as it is, colonial marines muddied it up and trying to add, or remove anything will jsut make things messier and more complicated than it needs to be.
The only problem i really see is , who all over in fox actually gives a damn about the Alien universe or us(the fans).