I know with the rooms they are changing the price per night depending on season or day of week. If you check in 2007 on the 2007 dining plan and stay till jan 8 2008 does the plan change to the 2008 rules on new years?
That's not really the choice people have. Many of us have contended for a while that the Dining Plan is underpriced, and evidently Disney agrees and has finally brought the pricing more in line with the value that can be derived from the offering. Regardless, I don't see how that's relevant to your OP.