I am definately under the impression that the "MacBook Pro" models will only come in the 15" and 17". The smaller size will be left completely for the 13" "Macbook". And following the typical Apple product lineup, it will come in the "Good, better, best" configurations, perhaps lower specced ones to suit students and casual users (Core-solo), and higher specced ones to suit more demanding users (core-duo).
After all, the current product lineup is a bit messy, with virtually no difference between the 12" and 14" ibook (even the screen resolution is the same!), and then barely any difference between them and the 12" powerbook. It is only the 15" and 17" where things get a little more exciting - backlit keyboard, bigger batteries, widescreens, brighter screens, better sound, sudden motion sensors, plus others.
I'd say that "much cooler" products are in the pipeline for the pro users.
Perhaps a pro subnotebook sans optical drive, and docking capabilities. Perhaps a tablet. There are many different scenarios, and this cleans up apples notebook range from 5 different models and dozens of configurations to 3 different models and less possible configurations. This in turn will speed manufacturing, improve supply/demand, and increase inventory efficiency.
Seems like a great move to me. So long 12" Powerbook.