I know that Wii-U will work with the original Wii games and hardware.
When I play original Wii games on the Wii-U will the game graphics up convert to 720p/1080p? Or will the system play them in standard definition 480p?
Nintendo made official statements about this last year in interviews that no, Wii U will not upscale Wii games. Those interviews date back to the console's original reveal, but as far as I know, Nintendo's stance on that issue hasn't changed since.