ADDED!
Hey Ryon over at Neogaf it's completely fine to transfer your crap to the WiiU, the Transfers don't take your homebrew junk just the official crap you downloaded through the Wii Shop.
Also you can back up EVERYTHING on your Wii before hand so you can transfer everything and when the Wii is done deleting your saves and junk, you can reboot everything back to your Wii like it never transfered.
It's real neat.
My question now is will my transfers stack.