DisneyGeek is right. We actually used that offer and it was wonderful.
However, I wouldn't hold my breath waiting for that to happen again soon. I really don't think Disney attracted many who would not have otherwise stayed with the offer. The 50th Anniv. did more than the
free dining to bring people to the parks, IMO. On the other hand, many of the people who took advantage of the free dining had already planned to stay there and pay for the dining package (like us). For my family, it was as though someone just said, "Oh, you're going to Disney in October? Then eat all you can, and more, on me! Here's a check for about $700 to foot the bill!"
I really doubt they filled as many rooms with that as they would with just a straight up discount on room prices, and discounts on room pricing, I bet, probably get Disney a better return for what they're not charging, than in not getting a single penny for my family of 4 for an entire week for all that overpriced food of theirs!
On the flip side, for those who would not be interested in the dining plan anyway, or who prefer to eat off WDW property, the free dining package wouldn't be as attractive to them (since this special came with a rack rate provision on the rooms) as a room discount.
It was awesome for us, but I just wish I could be a fly on the wall to listen as Disney's CFO hears the Disney return on the free dining last fall. I'm betting the CFO's outrage at the loss would probably kill said fly.
Yes, I'd look for a room discount well before the free dining.