For whatever reason, web designers Gifted Apollo went trawling on Xbox.com, and scooped up the image files for pretty much every Xbox Live Arcade game on the server. Even the ones that aren't out yet and which we know nothing about.
Like Star Wars: First Assault.
With no announcement or official word from Lucasarts on the project, all we've got is the platform, the name and the "box" art. So let's speculate!
Many are looking at the art and guessing that it's some kind of team-based game, maybe even a dumping ground for the work done on Star Wars: Battlefront III.
I can't think of anything better, or more likely, than that. Especially since plugging the art into Google Image Search gives you a bunch of Battlefront results.
XBLA [Gifted Apollo, via milkybar1983 @ NeoGAF]