It's hard to tell with Apple... plasmas with built-in computers would have been a huge revolutionary step, and just the sort of surprise that Jobs likes to pull on people.
But as I said in one of my posts, plasma TVs are NOT good computer monitors. The resolution isn't high enough and they suffer from burn-in far too easily. Also, the lifespan of a plasma TV will far exceed that of a personal computer... so you'd eventually end up with a plasma TV with antiquated computer parts inside it. Not a good idea. A separate computer module, linked to a big display, makes far more sense.