I think they still can relase Prom 2 and Alien 5 in the same year if they want.The year delay for Jurassic World is not affected the film, its not better maybe just become a bit discont budgeted as i seen the original concept arts.
If they start shooting Prom 2 im february it could wrap in april or mid may as we know Scott like to shoot fast his movies.So if Blomkamp's Alien 5 start shooting in june or august its still in time for a next summer relase..so i cant see whats the point with a year delay..they in pre production from march which was 6 month ago, and if they start filming next august/sept that amount of time could be enough for a director to finish script and prepping.The most biggest problem is our leadig heroes Weaver and Biehn are getting older and a year delay is not good for Weaver 66 ,Biehn 59.They will star in their legendary roles in a sci-fi action movie! Where is a respect to them if they have to wait for Prom 2 to be a succes? And what if its not?
By the way i like the interview with Ridley Scott just cant see whats the point of a possible delay.
Relase Prometheus 2 in March 2017 and Alien 5 in July or November,2017.