There’s an iPad market, and the iPad could be classified as a tablet, from a hardware-centric viewpoint. But the market for non-iPad tablets is about as big today as it was before the iPad, which isn’t nothing, but it’s close enough to nothing that Apple doesn’t need to worry about it.
Go read (or Instapaper) this right now. Marco’s dead on — the iPad is a stand-alone product, and the tablet market is just as sad today as it was a year ago. If not more so.