A booking including a dining plan is a WDTC package. (Unless you are a DVC member on points.)
There are WDTC ticketless packages for AP-ers. So maybe that is what you mean by a room package.
Generally there are room only bookings and WDTC packages.
They all include rooms. But a room only is not a package. It covers only a room reservation.
And a
DDP cannot be added to a room only res.
That is one thing nice about a package. Once the 2010 packages come out, and they are booked, they are pretty much locked in price. However, say you book a package, and things change, and you modify, rebook, etc, that's when prices could change (up or down from what we have seen here on the Dis). And the modifying will change to whatever is current.