The only thing working against them is hype. Halo had little-to-no hype, making it that much more amazing when it became a household name. Bungie now has a massive following, and a LOT of pressure to deliver. Also, it sounds as though Bungie is moving away from the Arena shooter and will be breaking all the rules of the traditional shooter. This will be great, but will no doubt upset some people. Not many people like change.