Both the email Pin Code and the hard copy pin code mailer I got over the weekend have "book by" dates of 7/28/12 for the free dining offers that start in October and run thru December (with obvious blackout dates).
It stands to reason that Disney may wait until the pin code expiration passes to get an accurate assessment of participation before they release a GP offering with the same discounts. This would also be consistent with 2010 and 2011 when they released free fall dining, which was late July or early August.
Its hard to be patient when planning for Disney, but I wouldn't get too worked up yet on not seeing GP offerings for free dining. Its only speculation on my part, but you may have to wait until end of July to see if it comes out. Hopefully not, but it wouldn't surprise me.