it is not possible for all countries in the world to ban bitcoin mining because all countries in the world want green energy and consequently that same green electricity will be used by miners, so it would not make sense to ban mining when there is green electricity, what countries will do is demand that the miners use green electricity in their operations, of course this will take years to happen, maybe even 10 years, all countries in the world are still not 100% ready to just use green electricity, that's why it makes no sense to ban mining from bitcoin, even 10 years from now it won't make sense
bitcoin doesn't need to move to POS, not even 10 years from now, bitcoin doesn't need to move to POS, as the years go by more green electricity sources will appear and miners will use