Will the female characters all suddenly sound different? If so, will there be a weird storyline to "explain" it? Like an episode in which a mysterious gas messes up the voices of all the women in town?
Maybe they'll just suddenly drop all the female characters who were played by Mary Kay.
Either way, the series will never be the same again.
Then again, maybe Mary Kay will come back from the dead with no explanation, just like Kenny has always done.