Yeah, the fact that, I think, Perrin used the term DVD but then Nintendo went out and made a correction to her statements later that day in changing her term to "12cm discs" shows that it could be anything. 12cm is the size of a DVD, BRD, and HD-DVDs. I doubt they'll be using regular dvds becuase of they were, why would they bother selling a add on to play dvds? If their games run off dvds, then it'll just be smart for them to make it a standard to watch movies.
I'm with K-rpg, I believe they'll go with their own custom variation of either HD-DVDs or Blue-ray, I'm leanin towards hd-dvd though as it doesn't benefit Sony in anyway. The fact that they'll then be selling an add on (I guess) in the future to allow you to view dvds could mean that they can provide a dvd player now for purchase and a hd-dvd player or a blue ray player in the future depending on how the disc battle goes.