They need to have an account system on the Wii U where all your digital purchases get tied to said account . Think about it, Sony and Microsoft have tons of users from XBL and PSN that have bought a lot of games for those platforms. For this people, upgrading to the PS4 and Xbox 720 is a good investment cause they know they have a library of digital games that they will able to play on those system just by using their accounts. Wii owners will have a more difficult process to use the games that they have bought on Wiiware and the Wii Virtual Console because those games are tied to the hardware. I think the Wii U uses an account system but I think we have not get the information yet on how it works.