This is never how you want to get confirmation for a story, but we do what we must. Ex-Obsidian designer David Kondor's LinkedIn profile lists his involvement in a "canceled third-person action Aliens RPG (Xbox 360, PS3, & PC)." The listing lends credence to rumors of the game's cancellation, which circulated earlier this month. We still haven't heard back from Sega for official word, but we've put in another request for comment this morning.
If you're curious about what might have been (but what almost certainly won't be), you can see more details from Kondor's listing right here.