Huge news from tonight's investor meeting: New Super Mario Bros. 2 will be the first Nintendo game to be available both in a physical medium and as a downloadable title. More games will follow, including Wii U launch games.
But there's a catch! Rather than selling the games directly to consumers, Nintendo is still using retailers to distribute the games, presumably in order to stay in a good relationship with them. The games can still be bought without going into a store, but you'll need to visit a retailers' website.
Here's slides from the conference comparing it to the normal digital distribution model:


And another detailing possible pros and cons of buying digital or physical:

This is a massive step up for Nintendo, and I'm surprised to see it happen before the next generation has even truly started. I think I plan to start buying digital as soon as it's available: my decreasing storage space will thank me.