It strikes me as extremely unlikely that any production model of the iPad is going to have carbon fibre componentry, at least for the forseeable future.
Given current technology it is impossible to mass produce carbon fibre components as cheaply as aluminum. The iPad's aluminum back can be stamped from commercially available coil aluminum in seconds, whereas CF components require lengthy processing in an autoclave. There simply isn't enough CF manufacturing capacity available to meet the aggressive (ie. Millions) production estimated for the iPad. Carbon fiber is also unsuitable as a material to receive screws or other threaded fasteners, and would require costly metal inserts.
The potential weight savings from using a CF would be measured in grams, not ounces. But it would several dollars to the cost of manufacture, which would result in the retail price increasing by $20-30 or so. It's not going to happen on a product aimed as the mass market.
