Hmm, I see. That does indeed seem premature. Ah well. is it anything important?
The first update is for a second playable campaign with a different character (Plague Knight); it's not out yet but it should be out soon and they've said it'll be included with the retail version.
Future updates include two additional campaigns (King Knight and Spectre Knight), a gender-swap mode and a local multiplayer battle mode (not available for handhelds), none of which will be included with the retail version--you'll be able to download the updates for free as they're released, of course, but they won't be on the disc/cart.
There's also a challenge mode that will be released piece-by-piece with the updates, so some but not all of the challenge stages will be included with the retail version.