I really don't think we'll see FF14 this gen.
Think about it: Earliest it will be end 2009 in Japan and then earliest June 2010 in the West. I expect next generation to start 2011 or 2012. A new Final Fantasy takes at least 3 years to develop. And in the meanwhile they still have versus to finish.
Anyway: it will not be on Wii. Final Fantasy is very much based on the graphics, so I really don't think they'll take a step backwards.
WiiHD could very well be possible though.