I agree completely. I don't think there were any
restrictions when the original plan was introduced, and I was certainly told more than once that yes, I coud order any appetizer, any entree, any dessert off the menu at participating restaurants.
And with one minor exception (the now infamous Baclava incident at Tangerine) that's exactly what happened during our 5 day stay in late May, and the plan added immensely to our WDW experience. AND, we spent more on souvenirs that we would have because we felt we were saving so much (that was our perception, not necessarily reality

)
When new restaurants were added in May, they
entered the program with a few restrictions. Fair enough. Anyone who had booked up to that point was not expecting to be able to go to Wolgang Puck's, so it would not be a disappointment to anyone to find out their favourite item wasn't part of the plan.
But, to use what I
hope is an outlandish example to make my point: If I pay for the plan today, which currently has very few printed menu restrictions, and then, get to WDW in December to be told, "Oh, we changed the plan, and now you just get cereal for breakfast, a hamburger, Coke and cooke for lunch, and a slice of pizza, cookie and Coke for dessert" I will feel very cheated and angry.
Would it be legal for Disney to make such a radical change to the Dining Plan? Perhaps. Would it be an ethical way to conduct business? I don't think so - not when the plan has been marketed to most of us as a great opportunity to try new restaurants without restrictions (other than the stated inclusions - one appetizer, etc.) I don't really believe Disney would do this, but others on this thread seem to be suggesting that they would have every right to do so, and as long as we still get fed something we should be happy!