25GB Proprietary Disc is the Only Playable Medium on the Nintendo Wii U
Similar to Nintendo's previous console the Wii U will only be capable of playing a proprietary disc format that is very similar to a Blu-Ray disc. In fact, the storage capacity for a single-layer Blu-Ray disc is 25gb which is identical to the medium that will be used with the Nintendo Wii U.
Nintendo debuted their new console at this years E3 and during the Q&A session, Iwata replied saying "Wii U does not have DVD or Blu-ray playback capabilities,".
I feel that most people's expectations at this point are already used to the idea that their Wii does not play DVD's — and are probably comfortable with the notion that the next generation console will do the same.
Keep in mind that there are other ways to play movies through the Wii like Netflix; so it's safe to assume that Netflix will be supported on the Wii U. Most people I know that use Netflix would be satisfied that the console is capable of that, but I know there are those that are influenced by features.
If watching Blu-Ray discs on your console plays that big of a role into your purchasing decision you should consider either getting a PS3, or a cheaper Blu-Ray player, because it doesn't look like you're getting it from Nintendo anytime soon.