I've been thinking about this along with the TV show discussion elsewhere on the forum.
On the one hand I don't think there's any need for a retcon. I initially hated what they did with AL III EN, but they did what they did and it totally fits. It might be a shit way for Hicks and Newt to go out but there we have it.
What really muddies the water for me is the abomination of Alien Resurrection. The big deletion and all that crap. I'd love to have that movie deleted because it makes its own internal logic work with the bullshit deletion and Ripley clones and all that crap, but of course wrecks it everything else (I bet they've dealt with that in the EU stuff?).
On the other hand, saying that Hicks, Newt and Ripley sailed off into the sunset and retired to a farming planet somewhere feels better. It serves a jumping off point for new adventures that has some connection to the old stories. I think the connection is key.
For instance - Superman Returns really felt like a sequel (threequel?) to Superman II. Even though there were different actors and it was many years after the event, it had that connection (the music, Lex's land obsession, Spacey's take on Hackman's portrayal, Routh's Reeve-a-like - it worked. Despite the rubbish costume and a mis-cast Lois).
The Aliens universe is huge and we know that the EU stuff has proven that you can have totally unrelated stories, but for me, I love a bit referencing and connection to the source.
So whilst we don't need a retcon - I'd like one. But that's purely subjective - I'm confident that retconned or not, there are more stories to be told on big and small screen.