SifJar said:
NO disc or WiFi update out there will brick you. Any disc update prompt is because either you have an old system menu and haven't updated in a while or you have a new system menu but for some reason you have deleted or downgraded IOS. There is very rarely any reason NOT to update from a disc. Unless you for some reason rely on having a downgraded or missing IOS (cannot think of any situation where you need to have either on your Wii for any long amount of time), disc updates are safe.
they have done in the past, mainly due to user stupidty.
do you remember the bricks that came about from people on system menu 4.0 that downgraded to 3.2, leaving a stubbed ios50. then they ran a disk update with 3.4 on it, which didnt install ios50 as it had a higher version number --> brick.
same thing could happen if you downgraded from 4.2 to 4.0 - 4.1 and ran a game with 4.0/4.1 update on it (eg. nsmbw with 4.1)