The rumors of an Apple tablet are quite amusing to me. While I believe that there exist prototypes of tablet like devices, I don’t see Apple jumping into the tablet market quite, yet (I may be proved wrong in the near future, we’ll have to wait and see). The market isn’t mature enough and I don’t think that consumers are ready to abandon their keyboards for a bulk of their computing. The combo devices with a flip around screen haven’t really become mainstream, either. Apple, of course, is ahead of the curve in some areas; I don’t think this is the year of the tablet.
Anyone that has ever had a behind the scenes tour of Apple knows that Apple works on lots of different designs. Many years ago, I interviewed with and was offered a job with the Newton group at Apple and got to see some device designs that never made it to market. If I recall correctly, there were at least a few tablets (larger than any Newton produced).
So the existence of prototype hardware at Apple means very little. I wouldn’t bet on seeing a tablet quite yet.