At the end of the day, we simply know too little about the film and people are complaining too much about the one thing that is a given and we don't know how he's going to pull it off.
I know I'm repeating myself but I honestly hope Blomkamp just simply ignores Alien 3 and Resurrection but not for the reasons which most people would think. I love Alien 3, and Resurrection could at best be described as... underwhelming but I need to reform my opinion on it again. I rather he wouldn't touch these films and attempt to explain them. I mean it could fit in with a timeframe between Aliens and Alien 3, but there is a two week travel from LV-426 to Fury-161, and Weaver's age.. is also a problem unless digital de-aging is done.
Another form of retconning is that he could go the easy way out, and that's with the dream or memory implantation route. Personally, I call this the Bobby Ewing route. Sure it's an easy fix and a lot of fans speculate that Alien 3 and Resurrection were hyperspace dreams but I find this.. to be a cop out. Also, as a casual fan of the Alien series, I would feel a little bit insulted. The whole dream thing is just a way of saying that Alien 3 never happened, but it did happen as a dream, but it never really happened anyway..
I hope when Biehn says is true, that Blomkamp simply pretends that they never happened. I don't want something contrived and easy as going the dream route. If this is going to be an alternative Alien 3, then simply just ignore the last two films and take off after Aliens.
Done, done, no harm, no foul.