How would I feel if that happened? Horrible! I hope that all the people in those areas will repent, even if they don't become Mormons, so that God will revoke that just as He revoked His decree to destroy Nineveh after they repented.
They won't repent and bow the knees to the rules of Mormonism. So, according to your scriptures, your God is going to come and slay millions of people who are trying to live their lives as they see fit. We don't need religions threatening us with death and destruction, thank you. Your God is a murderer, nothing short of Dark Age mentality -- filled with blood sacrifice and cult rites. According to your religion, I live in wickedness and your God is going to come back and slay me with fire and all kinds of nasty things. Do I look worried? Nope. Because he isn't any more real than the missing king's name in Facsimile No. 3. The Mormon God has been disproved, scientifically. But if you can tell me the name then perhaps you can start talking about Joseph Smith's inspiration. But you can't, and that must bother you. I'm glad it does.
Wickeness never was happiness? I've never been happier!! It's joy, real joy. Wickedness is just a name you Mormons like to pin on people and things as you seek to judge the world waiting for your Jesus to come and kill us. But your Jesus isn't coming back. And even if he did, I could never bow my knees to that monster or the Father of a monster he represents. They are gods of death, destruction, and religious intolerance. All made up in the mind of Joseph Smith.