Yes, I think in the chaos that would ensue once the shooting war restarted, a number of North Koreans might think, "This is my chance to get the heck out of here," and rush the Yalu.
Do you watch Vice? They had an episode on the North Koreans that defect to South Korea. It was pretty sad. They don't integrate at all. The world has passed them by. It would be like plucking someone out of the 1950's and dropping them in the middle of society today and telling them to get with it an contribute. It really would be a mess.