It's more than likely going to be 6 origins to start.
I definitely feel that Larian will follow the DOS model and eventually do an Enhanced Edition 1-2 years after the full game will be released. There will be more updates, patches, content for years to come.
It's been stated that there are 8 origins planned; and that during EA companions will be added. Could potentialy be non-origin companions, but I highly doubt 1.0 will release with less than 8. (They've previously stated they want all the companions to be available as origins, but seem to be reconsidering.)
I agree about the post-launch support though. From things that have been strongly implied (or outright stated), the first will be mod support and then DM mode. I'm also hoping for more player options.
