Somebody said in a thread, I read a few days ago (sounds like a poem)
anyway, that in the future, these films will be kind of like the Universal Monster movies, i.e. Dracula, Frankenstein, The Wolf-man and so on, they had terrible continuity, but they where all tied in together, cross overs and so on, and I am sure at the time people had these kind of arguments, since the continuity was all over the place. Or maybe they didn't?
But these days days, nobody cares but counts them all together as canon, maybe? and just enjoys them all, even the not so good ones, so in about 20 or 30 years, I don't think this canon stuff will matter anymore, they will all be in one big box set on 'Hologram Definition' or something and just labeled as classics, even the AVP films.
But this is the distant future we are talking about, in which there might be more Predator films, Alien films, maybe another Prometheus and a retry at an AVP film that might go down better than the last two, but still not as good, who know what may happen.