I know everybody is riding the TPM bandwagon but just let me assert that in order to do secure micro transactions, renting of games, preview of games etc. a TPM is not going to cut the cake. The TPM is valuable to store customer credentials and to issue keys.
What xBox needs to do all of the above is a secure execution environment! Maybe a secure card reader?
Will it have a secure execution environment? Possible!
"...Essentially an online store for purchasing game add-ons, new game levels, maps, weapons, skins, and even community-created content, the Marketplace will feature game and genre searching.
Micro-transactions. This feature will let game makers charge small amounts of money for in-game services and features, such as new cars for a racing title or new weapons for a first person shooter..."
... is almost a one-to-one copy of early WaveXpress demonstrations 3 or 4 years ago...