So, either Apple has nerves of steel and will risk simply not having any 2GHz's for sale between the time they run out and the time they release the new ones, or we should see wait times on the 2's grow in a fairly linear fashion between now and then.
Another couple possibilities would be an education-only version with a single 2GHz CPU, or perhaps the rumor is just off on the specs and the low ends will be 2's instead of 1.8's. (I hesitated to point this out, frankly, because someone will absolutely pipe up with the notion that Apple will be putting the 2GHz CPUs in Powerbooks... Hope springs eternal)