One day, and that day may actually never come, Intel and AMD and Nvidia and ATI will join the game (or some other really large chip company). Then we will see smaller Asics. Desktop sized machines doing 1 TH/s or DVD player sized machines doing 100 to 200 GH/s.
It's really just going to get smaller and faster, like all other technology. Just look at processors and graphics cards: compare one made today, to one made 5 years ago.
I highly doubt that. Intel and AMD would have no interest in doing so. If they did they would inflate the market to a point where nobody else could compete, and there wouldn't really be any more hobbyist miners.