At Nintendo's E3 press briefing today, the company confirmed that the Wii U will support a variety of video streaming services. Those include YouTube, Amazon Instant Video, Netflix, and Hulu Plus.
Netflix and Hulu were already available on the original Wii, but YouTube and Amazon are new additions. Presumably, the system will be able to stream the video to your TV screen or the separate screen controller. Release windows weren't disclosed, but the video services were treated as a given.