Regional French Dialects

I was wondering the other day how this will turn out after civilizational decline. Rome was a small town and Italy a multiethnic peninsula . Later latin was standard and after collapse dialects ensued until the 19th century reunification, standardized schooling, newspapers, TV, radio. Similar has occurred elsewhere. Chinese now have turned to Mandarin for example. If society collapses due to loss of energy, electricity then decentralization would mean that each generation invents new slang, takes it on and after a while dialects emerge in each small zone on earth, separated by natural barriers. Maybe later a new empire arrives to make some dialects a centralized lingua franca.