A tweet from Alien Isolation says that the version of Alien Isolation shown with the Oculus Rift at E3 was just a prototype, and that Creative Assembly does not have a full VR version of the survival/horror game in the works: "What we've got at the moment with @oculus is a prototype, there's no full game in dev :)" Eurogamer has a statement from SEGA indicating they agree the Rift demo of the game is awesome, so they are very excited about not making a full version. Here's the mixed-messages explanation, which a cynic might take as a solicitation for some Zuckerbucks:

At present, it's just a prototype and does not represent a game currently in development at this point in time. It's a truly amazing experience though and brings the game to life in ways we could not have imagined when we started the project. It's one of the most terrifying demos you'll ever play.