There is much speculation going round at the moment as to whether the Wii will support High Definition output later in the consoles life.
Here's a recent quote from Reggie Fils-Aime regarding the topic:
"Tough choices about not including a DVD player at the start, tough choices about not including high-definition capability at the start. That's because we wanted a mass-market price, and we believe the market will validate those decisions come launch day on this Sunday,".
To seek further clarification, gameinformer.com got in contact with a Nintendo rep who said that although such an accomplishment wasn't impossible, Nintendo have no current plans to upgrade the maximum resolution from 480p.
The rep went on to add that Microsoft was able to patch the Xbox 360 to support 1080p.
After all, Nintendo has already released a patch to allow Wii gamers to transfer game saves to SD cards.
Link: Game Informer Online