I was wrong. Nintendo Network is more than a re-branding of Nintendo Wi-Fi Connection. It's not a huge, Xbox Live-like system, but there is new stuff on the way. This is how Satoru Iwata explained it at an investor meeting:
...for the Wii U, we are planning to introduce a personal account system compatible with Nintendo Network. With this, for example, the ease of using a video game system when the hardware is shared by multiple family members, which has been a challenge we needed to tackle, shall be improved, and we will also be able to construct and offer the system by combining a variety of different services and content.
And this is definitely a step in the right direction.