I think Fox have seen the poor reception Terminator Genisys received (i know fox no longer have the rights) in the western box office (even though it performed better in china) and have got cold feet at the risk of doing either a retcon or alternate timeline approach to the Alien franchise. This coupled with Blomkamps recent films not exactly performing as expected and fox is a business, they would put the project on hold and place more emphasis on Scott with his prometheus sequel, after the success of the martian.With Ridley going back in the direction of exploring the alien franchise too, i think the studio will invest more in that, Scott has a story to tell and the studio seem to like it. I for one would much prefer to see a prometheus sequel, which explores the xenomorphs origins and the engineers more, i'm looking forward to alien:paradise lost. If there is still a link to Ellen Ripleys character, i think it will either be the nostromo or another character related by name.