The fact that they are kuffar doesn't necessarily mean they will be killed for that. It's entirely possible that they could be free if they recognize the Islamic state. The Mughals in India didn't exterminate the Hindus and didn't even tried to convert them (and the result today is a fascist Hinutva regime that justifies and encourages the rape and killing of little girls just because they are Muslim, see the Asifa case).

