You can use usb memory devices now, it was in the last dashboard update. I guess they planned this cause they knew the new slim was coming.
You will also be able to buy the data transfer kit still to move stuff from your old hard drive to the new console.
The console will be onsale at the current Elite price of £199 this has been confirmed.
Here are some unboxing photos. Looks great and the hard drive is internal but still a special 360 casing around the drive.
http://www.engadget.com/photos/xbox-...ing-0/#3077086