Theory- Who is the next villian in Demon Slayer?

I have a theory that if they really do manage to kill Muzan in this arc and eradicate the demons. If the story continues afterwards, that the Demon Slayer Corps. will disband and the government will be the next baddie. It was said the Corps. was never officially recognized by the gov. and that once they disband the government will use that chance for a power play causing corruption. The story will then be about slaying the demons within ourselves instead of actual ones. But take this with a grain of salt. 

Theory by Reddit user PipiplupShinobu