Ripley had already died at the end of Alien 3. I don't see or get what Sigourney meant by returning to the Alien movies. So now what? Some possibilites just came across but they would still be terrible to explain why and if Ripley is still alive or if Sigourney Weaver comes back to repise her role as the Eighth Clone (Ripley-8) from Alien Resurrection. Maybe it will be an Alien+Aliens reboot remake of sorts?
Oh or maybe a nother bogus excuse, oh btw now Ripley has a "twin"
Otherwise maybe some other bogus retcon excuse they'll write in the script to try to throw out Alien 3 and Resurrection and treat them as if they were just really long bad dreams or "premonitions" Ripley had? This had been considered way back at one point if I remember that Alien Movies FAQs.
Maybe time-travel of some sort that alter the events therefore whatever we had seen Alien 3 and Resurrection never "actually" occurred, or thus creating an "alternate timeline and/or universe".
Think it would be an easy fix and retcon to resurrect a character killed off right? I very much doubt it, and I bet most people here have the same opinion regarding such attempt. Maybe if they had gone that route in the first place without the terrible Alien Resurrection story, but even now I think it would be far far too late.
The already attempted to "undo" Hick's death with the Aliens Colonial Marines video game, which wasn't very believable and had way too many continuity mistakes.
Perhaps the story has something hinted or splashed in regarding the Engineers (Space Jockeys). Maybe they have some form of biotechnology that could resurrect chestbursted victims
Either way I am lost on her for this one, but hey in time we will all see what she actually meant.