I haven't heard anything about this, and I've been keeping pretty close to the news on the series... KH Ultimania isn't saying anything about it either (warning: dun go there unless you have a good virus scan, since mine keeps saying there's something on it)
There were big rumors back last year that there would be one for the wii, but nothing definitive. There were
[ trailers ] and
[ scans ] 'leaked', as well as fake scans and articles from Nintendo Power, but everything was debunked.
In an interview with Nintendo Power:
"NP: Have you given any thought to bringing Kingdom Hearts to Wii in some form?
TN: Once the projects[birth by sleep, 358, coded] I am involved in have settled to a point, there might be some room to consider that. But at the moment, I've got my hands full."
There isn't anything ruling it out, but there hasn't been any evidence yet it'll be on the wii. Most likely the next game won't even start until a year or so after Birth By Sleep comes out :I