If you have a modded Wii you can make your own Wii dvd discs anyway with the Wii Media Disc Creator, just drag your movie files into the folder, create the iso, burn and stick in the Wii and enjoy the movie.
The current Wii only needs some type of software update to play actual dvd discs, the dvd drive is capable of playing them but the software on the Wii just don't know what to do with it, a simple DVD channel update by Nintendo would sort this out, no need to make a whole new console.
If they release a whole new console then its just about making more money when they could just charge some points for a DVd channel download.