Most people are speculating that it's a 20D replacement. The product cycle for the 20D is about up, and it's prices have been dropping, which is usually a good indication. You can probably expect an attempt to step ahead of the Nikon D200.
There's always a good round of rumors. I've noticed JP has been very quiet lately. He always seems to have a pretty good idea what Canon has up their sleeve.
Personally, my bet is on a 20D replacement with a 2.5 inch LCD, 10 to 11 megapixel, 1.6 crop, tweaked AF, and more noise reduction at higher ISO. An incremental upgrade without stepping on the 5D's toes. We'll see. For me, the price drop on the 20D was too good to pass up.