Let's see, if we accept the idea that Ripley and Hicks are going to be brought back like in the concept art we've seen so far, that A3 and A:R will not be "undone" and the Ripley featured is NOT Ripley 8, as we've been told, there are a limited number of options for where Blomkamp can go with Alien 5.
1. Ripley and Hicks are clones/synthetics. When the comics were retconned after Alien 3, this is how the writers justified Ripley being there. They just made her a synthetic. I honestly don't remember who made her or why. But it has been done before. Technically, they don't have to clone Hicks if the follow Aliens: Colonial Marines. So they COULD keep it all in continuity if they make Hicks an older man long after the events of Alien 3 and have the Company make a Ripley synthetic. Cause 'reasons'.
2. This is in interquel, taking place after Aliens but before Alien 3. How they would justify Ripley and Hicks aging, then Ripley DE-ageing, I honestly have no idea. This is honestly just a ridiculous idea, IMO. It makes no logical sense given the age of the actors, and frankly it wouldn't have much room for story. There's very little freedom, and frankly we're going to know how it ends. Ripley, Hicks, Newt and Bishop all in cryostasis on the Sulaco. No mystery there. No suspense. Boring.
3. Time travel. Wormhole, a new invention, the arrival of Q from Star Trek. Absolutely the worst idea of the bunch, but it is there.
4. Alien 3, Alien: Resurrection and Aliens: Colonial Marines will simply be ignored. Not undone. Not put into a dream sequence as if they were a delusion by Ripley/Hicks/Newt's traumatized brain, no shot of Bender Bending Rodriguez showing up and telling the audience "In three seconds, you will forget that the Alien franchise was screwed up by idiots, then brought back by bigger idiots." Nope, those films will just be ignored, and Alien 5 will simply be an alternate future that Alien fans can pick up or put down as they desire.
I can't think of any other way that Fox and Blomkamp can bring back the Ripley and Hicks and not have Ripley being Ripley 8, something that has been categorically denied.
Can we, as a fanbase, primarily agree that the 'ignore' option is the best option, IF Ripley and Hicks must be brought back? I think most of us can.