Quote from PiccoloCube:
btw, updates for games should be deleteable. i hope they aren't tied to your savefile (i bet they'll do something evil like that and force us to lose our saves if we refuse the update and want to get rid of it)
I don't really see many 'updates' to games occurring given the limited amount of storage space on the Wii. If you are really concerned, you can always back your save files up on a memory card before updating.
This isn't like updating a PC game where you have many gigs of space to work with.