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.