I think John Davis said a sensible thing and that is to let it rest for now. That, or invest serious talent and money into the franchise instead of the water-testers we got since AVP.
Decent actors, better scripts, good SFX studios with a proper prep instead of rushing suits out ASAP. That's all we ask for.
Box Office sucess controls the likelyhood of seqels. I don't think AVPR really justifies much more. However with the new ailen preqel in the works (Prometheus) I guess we'll just have to wait and see how that does. If they find people are clamboring to the theaters for it - maybe FOX executieves will start to think about about what other 'alien' series they can ressurect again.
I've always hated the aliens, and only tolerated them in the AVP context, but I was looking forward to the prequel. Maybe this will really be the birth of a whole new franchise. We can only hope, but somehow, I don't think Ridley Scott will disappoint us.