I posted a story idea I had for what I thought Blomkamp's direction may go with the script. In it I proposed that Weyland personnel boarded the Sulaco shortly after the events in Aliens and did some type of dna extraction process where they made clones of the characters which they then put back on the Sulaco to "cover their tracks". This would still validate the Alien 3 and Resurection movies though I can't stand them.
Anyways, due to the tech Weyland used, it *aged* the characters significantly because of growth hormones/etc during the dna extraction of them. This would explain their aging *if* the story picks up shortly after Aliens.
Weyland has the *real* Ripley, Hicks, Newt and Bishop in a secret facility. Weyland brings Bishop back on-line and re-assembles him. He manages to break Ripley, Hicks and Newt out of their forced hybernation chambers with news that he's detected a distress signal coming from LV-426......
Lance also was joking around at the SDCC Panel by saying that Bishop has the ability to age with his human counter-parts as to not make them feel odd/isolated, whatever. I thought it was a neat idea.