I have to agree with Jim.
Not for a looooong time to come. It’s going to take a minimum of 20 years, if not more, for the ROK to bring the DPRK zone up to the same level as the South in terms of infrastructure, housing, health care, and industry. Look at how long it took a reunited Germany to get the East up to speed. It’s going to be ten times worse for Korea — not even taking into consideration that a good percentage of the population is full gonzo NUTS.
Someday, they might cause Japan to worry. But it won’t be in my lifetime, that’s for sure.