If the iPad is successful as an interface in its current relatively limited role, I could envision Apple moving the ball down the field and bringing out an actual tablet running OSX with a touch interface at some point in the future.
Yes, there are already such Windows devices out there for that, but touch interface has been a major thrust for Apple over these last few years, and I have the impression that someday they'll have it functional enough to make it work far better as an actual computer than the largely failed niche devices from Fujitsu etc.