While Zelda is unlikely to be DSi only, it is VERY likely to be a DS/DSi combo game that looks a LOT better on the DSi than it does on the DS.
While on that Zelda note... lets say Nintendo announces a new Wii HD this year at E3 -- a Wii with 720p output, and faster internal chips/more memory (much like the DSi over the DS), and new "combo" discs for the Wii/WiiHD to both play (the game will autodetect your system type).
Right about then, we'll also see a new Wii version of Zelda announced. And guess what... it'll be one of the very first WiiHD/Wii combo discs, and will absolutely blow us away on the new HD Wii.
What better way to get people to upgrade, without upsetting their current userbase? Nintendo has done this for decades, and they turn a profit like clockwork. Its not a surprise anymore.
