Shinichi Manaka , Microsoft Japan Xbox platform development chief, revealed in an interview that the Xbox 360 won't offer support for current-generation Xbox controllers. He says they won't connect, and Microsoft has no plans to support them.
He claims the Xbox 360 is designed to be wireless, and they would like everyone to get use to this new gaming environment. He further adds that once you get used to wireless you don't want to go back.
NOTE: Microsoft has repeatedly said that the 360 will support wired versions of its controllers--which must be purchased separately--through the console's three USB ports. The console's wireless controllers will also be able to be hooked up to the console with a cable while recharging.
More info about the technology behind the wireless Xbox 360 controllers at GameSpot