Creative Assembly, the developer best known for the Total War franchise, is working on a new game based on the Alien franchise. Other than that the new title is being developed for Sega, we don’t know much more about it yet.
As for Creative Assembly, they will be opening a new 10,000 square foot studio as part of the development of the project. Currently, they have about 160 employees and they expect to grow that number to about 200 once everything is in place.
The Alien franchise has not had a lot of luck getting titles to release. After Sega acquired the rights, they commissioned an Alien RPG title to be developed by Obsidian, which was canned way back in 2009. In the meantime, Gearbox is said to still be working on Aliens: Colonial Marines which is an FPS title that has been in development for a long time; but reports indicate that the title is still inching closer to release.
Expect Sega to make a more in-depth announcement of what the Aliens title is, along with a projected release date during E3.