Speaking recently to GameInformer.com, Peter Moore said that Microsoft "will probably be in a position in about two weeks" to post a list of Xbox games that will  be playable on its next-gen console at launch on Xbox.com.  No further explanation about how many titles this will include was mentioned. 

Moore continued, saying that the compatability list "will grow and grow and grow" and will "get updated as more and more games get through certification", suggesting that the company may be planning a larger backwards-compatible catalogue than previously expected.