A few random thoughts here.
Wouldn't it be a head trip if sometime in the future, we heard news that Cameron was in talks to return to this franchise. Ridley did it, so why not Cameron? If Cameron did though, would it be in the same style as Aliens? I can't see him doing anything else.
In regards to bringing back characters like Ripley and such, is it really necessary that her character or anyone else from the old movies be involved in any sequels to the original films? If that happens, and they retcon anything, are they basically saying the series revolves and can only truly exist around these particular characters? I really hope that's not a direction Disney chooses.
The idea of any future Alien films being made in the same spirit of Aliens is a hot button issue to say the least. While I personally prefer a lone alien doing its thing, wouldn't a sequel in the 1986 style be the natural direction the series was progressing? We went from a handful of people on the Nostromo to colonial marines dropships, planet colonization, Alien queens etc. It really was a big jump. To go full tilt Alien 1979 again would have been one heck of a slowdown. Had the transition been gradual, it may have been different, but Gibson's Alien 3 was (I think) a more accurate representation of the natural progression.
Perhaps, the fallout of Ripley's death and the events immediately following it are the proper way to go for Alien 5. Hicks and Newt would still be dead as well, as would Bishop. You have the opportunity to go Alien 1986 without rehashing old characters and storylines. Wey-Yu is panicking at the death of Ripley. Send in the Marines with some science officers to try and recover a sample from the original derelict. We'd get to see more of the cave system. Maybe the movie revolves around their survival in the derelict, maybe things go bad back at the lab and the film ends on a cliffhanger with a grown Alien escaping into the vent system at Wey-Yu. A bloody and mutilated grate is seen on the wall, as science personnel stare at it in horror.
A slower film could involve a crew dispatched to search for the Nostromo, with disastrous results. They find the derelict and never make it off the surface. Whether the fight for survival is fought in the derelict, the caves, or inside their own landing craft would be up to the writers. Heck you could even include a quick scene of them finding David's remains, a little nod to the prequels. Either way, we don't really need to have Weaver around to make an Alien film. There's a lot of good characters out there just waiting to be written.