unless this rep misspoke, that is:
"AM: ...the GameCube discs will not be compatible with Wii U, but a number of the games that were playable on GameCube can be downloaded from WiiWare."
- http://www.nintendogal.com/2011/07/19/nintendogal-com-interviews-amber-mccollom-e3-2011/7180/
you know what that means: 1080p uprendered windwaker. probably.
Still not exactly on par based on what it SHOULD look like 'colorwise' with a component connection, but it's vastly superior compared to the supremely bogus dark uncolorful emulated crap that's been churned out by Nintendo...