In 2011, Sega and Creative Assembly announced they were working on an Aliens title and bar one blurry monitor screenshot from a team photo at the CA studio, we've seen nothing of it since.
However, in an MCV [print edition] interview, Sega's European boss Jurgen Post said, "Aliens is still one of our pillars. In May 2011 we announced that Creative Assembly is doing something with that brand - we've said nothing else so you have to read between the lines there."
Ok, that makes it sound like work has ceased, but Post went on to say, "But it's a great IP, and very rich. Colonial Marines, although it didn't review well, did sell well to start. So there is an appetite for Aliens. Going forward Creative Assembly is a good quality developer and our aim is to create a good quality game."
Post also confirmed that Creative Assembly's game is being produced "...in-house so it's easy to manage the production of it."
If we were to read behind the lines of that quote we'd say Sega are keen to make sure they don't get screwed over again as they did with Gearbox ditching most of Colonial Marines' development to Timegate. There's no way Sega can afford to release two terrible Aliens titles in a row after such lengthy development periods. Not to mention consumers will be very cautious since being outright lied to in the build up to the last game.
You'd have to assume Creative Assembly are making something more in-line with an RTS like their highly successful Total War games, as their action titles like Viking: Battle for Asgard and Spartan: Total Warrior didn't do particularly well.
Years ago, we were hearing all sorts of rumours, everything from a horror title set on the Nostromo to an action RPG. We discovered that CA are currently advertising for a 'Digital and Community Manager - Alien IP' on the jobs section of their site, so perhaps we can expect to see some concrete details soon.