That is a very good question, Karrde. I can't wait to find out the answer. But I, like you, feel it will probably be one upgrade card per upgrade icon on the ship card.
The thing I thought was really cool was R2-D2's ability. I assumed all along that you would have to roll a certain result on the dice to regenerate your shields, but instead, you increase your current shields by 1 (up to your maximum) when you take a green maneuver. I love how this affects which maneuvers you'll take. I think the green, white, and red maneuvers are brilliant, and I'll be excited to see what other cards interact with those different difficulties.
EDIT: The other thing that struck me was the apparently few amount of upgrades in the Core Set. I'm betting that the limited upgrades is one of the ways they're hoping to sell multiple core sets to the same people.