And even then, I bet there will still be canon wars. The people who invent the canon don't even follow their own rules.
It's hard to remain optimistic for me. Not even because I'm against the retcon, which I am (of ALIEN 3 only) but because I just don't think Alien 3 or 4 are bad enough, or should I say, I am apprehensive that they can make Blomkamp's ALIEN film better than both of those films, enough to warrant a retcon. So, oddly enough, it's hard for me to say 'Yes, that's a justifiable idea!' because I have yet to hear the idea that FOX and BLOMKAMP think warrants a retcon.
Are you all convinced this Alien film is going to be better than the last 5? I am fine with A3, and PROMETHEUS. But if I had to take a shot in the dark, based off BLOMKAMP's previous films, I would say the only Alien films I am sure he can do better than are A:R and the AVP crap fests.
Of course, its absurd to expect to read a script and have this question answered but a central concept, not so much. Eventually we will have some idea as to what makes them all so eager.
In regards to whether this can still fall through, and Biehn's report of never having read a script or receiving an offer, I would almost guarantee that someone at FOX will be asking BLOMKAMP to try and find a way to NOT explicitly ( EXPLICITLY being the keyword ) undue those films and then they will decide how to proceed based on his ability to do so.
I say this because it's no skin of their back to request this, and the producers will try to come up with something themselves.
Still, if they are going to bring Hicks back, EXPLICITLY, then they may as well retcon it.