Considering the success the last 2 years, I'd expect this to continue in 2007. Last year we (AP holders) got our invite to buy tickets in April. They had about 10 dates available and you were allowed to order 6 tickets for each night per AP. We took 8 friends, 4 adults & 4 kids along with DW & DS. About 90 days before the event, they put the remaining tickets up for sale on-line. Last year Disney VISA card holders got about the same lead time on ticket prices. I think the early purchasers also got a discount ($5/ticket I think).
They changed it a bit from the year before, so I'd expect a couple of changes this year (maybe add a parade). Our primary complaint was a lack of places to find food. With 5 hungry toddlers and 6 adults the best we could come up with at 10pm was the Hot Dog place in the back-lot area.