Where does this leave the Xbox 360? remains to be seen?

This statement amounts to Sony playing catch-up with MS. AFAIK, MS has always had a policy concerning interoperability of 360 peripherals and didn't have the same controversial issue that cropped up on the PS3. (GH guitars not working in Rock Band) This isn't a leg up for Sony, they're "still working" on issues that MS never had and may never have, maybe Sony could gain an advantage by forcing "retroactive" compatibilty*, but how much mileage will you get by making sure that your Rock Band 2 peripherals will work with Guitar Hero 2?

*first they have to get the present sorted