Joystiq's #8 game of the year Peggle on your Xbox 360. A search of the latest ESRB ratings revealed that casual games Peggle, Ultra Bust-a-Move and Bliss Island were all rated for Xbox 360. Now one could infer that this means the games will be XBLA titles, but they could very well be retail products and Ultra Bust-a-Move may be an Xbox Original.
There is currently no release information, just that the games have been rated M ... no, kidding, they were rated E. Although that gives us the horrible idea for Peggle with adult themes and noises, perhaps with the orange pegs being cherries -- think about it.
[Update: Peggle has been confirmed for XBLA.]