"Historically" is relative. The MYW Dining Plan has only been in existence since January 1, 2005. It's only be free for one time period (in the past) so far, which was August 22, 2005 through October 4, 2005 (but as long as you checked in by that date, you could get the free dining for up to ten nights). There were two chances to book that - one beginning later than this but with about the same deadline, and again for about three weeks in July.
Anything's possible, but if you base it on history, no, there's NO history of the Dining Plan being offered free at any other time of year.