Colonialism added a whole new dimension to ethnic division. Then came the European Wars where Peace Treaties created many artificial boundaries. With its long history, ethnic strife has become a way of life in almost every part of the world. Ethnic strife also survives along other fault lines of division such as racism and regionalism. Custom, class and education also separates people.
Further conflict arises between urban, suburban, and rural populations.
Probably, but with ever diminishing intensity. Each subsequent generation will be better educated and more in contact with the whole world through electronics. Knowledge and communication promote tolerance and understanding. The eventual weakening of ethnic strife will come about, if at all, by economic advances. Economic growth promotes more education, more mobility, more communication and more common interests.