Unless you're staying on DVC points, you do need to get the Dining Plan as part of a package: hotel, admission, plus dining.
It isn't clear that there would be any advantage in booking a room-only, unless you would intend to stick with room-only if the package was never offered (it most surely will be), since, unless things change next year, at the time you book the package, there needs to be package inventory available. So you'd have just as much ability to book the package whether you held a room-only reservation or not.