Apparently in November of this year Nintendo plans to replace Wii points with a new line of cards going by the title Nintendo Points. These new cards will be released in Japan and be able to work with both the Nitnendo DSi, and the Nintendo Wii.
It should be noted that once you use a Nintendo Point card in either system the Wii or the DSi, you will not be able to switch the balance to your other system. The points will be stuck on the system you originally used the card on. So if you used it on the DSi, you better enjoy that DSi shop. So when the DSi actually launches here in the States we will be seeing these cards as well.