^I've already had Homebrew channel removed for a w hile now, and really don't care to install anymore of this.
But upon looking at the wikifacts of Bannerbomb homebrew and the official Nintendo release, it doesn't appear your Wii will even be "bricked"-it simply removes/disables homebrew, it doesn't render the Wii unplayable. Still, I'm keeping my Wii off for now until i get that confirmed, but 4.2 would wreck anything.
Edit-Just so you all know, after removing the homebrew channel and not running/trying to open the SD card from which you originally obtained the code, all that's "left" behind is a banner ID, which the update has no effect on. So simply removing HBC solves all the problems. Or just wait for 4.2U. Whichever.