So yeah, it's not a big surprise or anything, but it is a big deal to a lot Wii owners out there: the new Wii System Update 4.2 de-installs the Wii Homebrew Channel, and blocks most methods of reinstalling it. Anyone who values the ability to play import Wii and Gamecube games, Homebrew-only games like Portii, or any of the other various applications and emulators that the Homebrew Channel provides may want to stay clear of new Wii games for a little while.
The silver lining is that the recently released Dead Space: Extraction doesn't force the upgrade on Wii owners, so there is no pressing need this week to choose between new retail games and that old homebrew magic. The other potentially bright side is that according to Wiibrew.org, there may already be a fix to the problem. The latest of many Wii homebrew installation applications to hit the interwebs, a little bundle of code called Indiana Pwns, will reportedly allow for Wii homebrew apps to work most of the time. I'd test it myself, but I don't own Lego Indiana Jones, and that's something about myself that I don't plan on changing unless I absolutely have to.
So, in short, there is reason for Wii homebrew enthusiasts to be worried, but not that worried, or as Nick Chester said- "Doesn't this happen with every update and then 20 minutes later someone fixes it?"