I didn't see anyone address the question of what Imdaar Alpha was. It was the pre-release tournament for Wave 4. It was effectively a lot like Armada's Massing at Sullust tournaments in that the final round was played with the soon-to-be-released materials, which some of the top-scoring players were allowed to take home, giving them about a month to play with those before everyone got them.
I attended the one at Guardian Games (Portland, OR), and while I don't know the exact numbers, I'd say there were about 12 players there.