I got a PIN last weekend that was essentially the same as the current promotion except that I can book it through September 12. You might have already known about that though.
It is practically the same as the current public promotion but it opens up a few more opportunities.... Like we were able to get free dining at pofq which is not included in the public offer
The PIN codes can come via email or snail mail. It's a total mystery how people get them, but some suggest signing up for an account on Disney's site, requesting custom maps, requesting the vacation planning video, putting a planned "trip" in your online shopping cart without confirming/booking. Some people even just call in to the WDW-stay (play?) phone number and ask if there are any codes associated with their account.
Mousesavers.net has a good chart of past disney discounts for the last several years, what type of discount, when it was offered, what the necessary travel dates have been. Many people are warning that Disney has declared it is trying to scale back on discounts so, of course, past discounts are no guarantee of future ones. http://www.mousesavers.com/historical-information-on-walt-disney-world-resort-discounts/#codetrends