I am glad to see a stand alone alien film again, regardless of when it will actually be released. (After Prometheus 2, so presumably 2017?) I can see a possible route to a sequel to Aliens which would not erase Alien 3 and Resurrection from the official canon, but it does raise some issues.
Neil has stated that the new film would not undo the events of Alien 3 or Alien Resurrection(retconning them as hypersleep nightmares of Ripley or anything to that effect). Thus, i got to thinking about how this could be balanced. The one notion that came to mind would involve the events of this film to take place between Aliens and Alien 3 in the timeline. (Which may or may not have already been hinted at in the various interviews regarding the new film)
To to do this though would require that Hicks and Ripley wake up from cryosleep sometime after the events of Aliens, but Newt and Bishop are left in their cryotubes for the duration of the film. This raises the issue that others have brought up in other topics here, mainly the fact that Michael Biehn and Sigourney Weaver have noticeably aged, making it hard to explain how the characters they are to portray would have apparently aged as well. If the "something gets messed up with their cryotubes, but not for newt's or bishops" route is to be taken, it wouldn't make sense for she and Hicks to be found in them once again during the events of Alien 3's opening sequence.
With Hicks the cgi burns on his face and makeup and digital effects could make him look relatively younger, but It'd be pushing it with Sigourney(no offense to her as she is an amazing actress and still looks decent for someone in her 60s).
But with that potential problem aside, a plausible film could indeed take place and do very little, if any damage to the established canon of the alien film universe. All that's needed is for Hicks and Ripley to survive the events of this film and have the events which Alien 3 opens with follow said events. What this can do is give a plausible way to have another alien film, which could include a return to the post-atmosphere processor devastated lv-426, and do the nifty trick of explaining how that egg got there in alien 3, which has always remained a convenient, yet unexplained plot device for that film.
It is also my guess that the film will most definitely not go by the title "Alien 5". I suspect it will Aliens: insert subtitle here. Aliens: Epilogue or something along those lines.