>>8
2015: Kim Il Sung dies and his successor is a military dictator receptive to Chinese economic aid.
2015-2020: North Korea increases trade with China supplying cheap labor and natural resources, border controls with China are more liberalised.
2020-2030: An educated middle class develops to deal with an increasingly sophisticated economy, many of whom have extensive contact with China and push for a more open government. Since North Korea is only a shade less authoritarian than China they will probably agree.
2030-2050?: Eventually even the hardliners will be seen as more of a liability and quietly neutered by the new elite in favor of economic reforms that allow trade with South Korea.
2040?-2060?: 100s of people sneak into South Korea each day, the political elite will feel that re-unification is inevitable and may accelerate the process in order to secure their holdings after the re=unification is complete.