Kevin,
In talking to a well placed source, poa annua will inevitably creep back into the greens. In fact, it already has in a couple of small spots, this was most noticable on the practice putting green near the golf shop/1st-10th tees.
The belief is that the greens will eventually become 1/2 bent and 1/2 poa.
As far as the greens being firm....I think it has to do with both issues that you mentioned. New greens always seem to be notoriously firm (see Seminole last year). The greens at SFGC were the polar opposite of everywhere else I played during the trip...whose greens ranged from soft to downright spongy because of them being almost entirely poa.
The issue that was addressed at SFGC is likely to also become an issue at Cypress Point soon, as the appear to have the beginning of a nemotode (sp?) problem as well.