well i still think headsets will be supported for brawl BUT
they should just have parental controls on wii to enable voice chat someone had a mock up of the wii home menu when you press the button it had like headset enabled disabled nd volume. it should just have a password input to unlock it.
EDIT: pokemon diamond/pearl had voice support and you could choose whether you wanted to use in it your battle. i dont see whatthe big deal is.