tom's hardware just sent me a message asking if I'd select a 'best answer', so I'll rejoining the conversation to share we're i'm at.
The kind of question I was asking is one of technology forecasting, and product roadmaps I suppose. I recognize that it might be unlikely that people who would have this sort of information would be likely to share it. At the same it it's possible to construct this sort of picture… and that's what I'm looking to hear back about - does anyone know something about this or point me to a resource for this sort of thing. As an example of what I'm talking about take a look at this buyer's guide for apple products: http://buyersguide.macrumors.com/
from what I can tell the Seagate Momentous XT was first released in May 2010… maybe I can wait till may & get something like a 750GB drive w/ a 16GB SSD component?
anyway, wikipedia's page on hybrid drives has been the most helpful here by pointing out that hitachi will be bringing to market some hybrid offerings this year as well…