Here is a remark Greg made on imdb on the production on AvP3, if it does happen.
Well, Colin and I are not the final authority on this, but that would be our preference. The problem with movies that take place in space is cost - they require huge budgets, and are hence quite risky. There have been a good share of big budget sci-fi bombs over the last few years... but ultimately it will depend on the sucess of AVP2...
I trust them with making AvP3, and i haven't even seen the second one.