What Disney should be offering is promos like they did with the Costco SoCal offer..
Offer bundles with free 'Disney dollars' for buying tickets that need to be used within the time window. Throw in $100 in Disney GCs for buying a 4 or 5 day pass.. or something else strategically picked to lure an 'extra trip' out of their key demos and that should work.
Promos on AP purchases are a bit funky.. they don't lead to much immediate impact.. It's about locking predicted money in for the next 12 months... and many of your demo that would buy, are already on a cycle that isn't compatible with your promo. So I agree with Len's take, this maybe more of a hedge move than a 'boost' move.
I do think the throwing in Disney bucks for multi-day tickets (of the strategically picked type) or room discounts are far more attractive to people for getting them off the fence and adding another unplanned trip. Maybe room discounts are the best since 1) they don't cost anything and 2) are compatible with both AP and adhoc ticket buyers.