Even when they can hit everywhere on this planet, their limited budget and production capability will not allow them to produce more than a few of these missiles as well as the payload. There is not much of a concern. It is not like the Fat Kim Dynasty is actively seeking suicide. They just want to be left alone while ruling over their people like Kings... wait, they are kings. On the top of the unrealistic goal of absorbing South Korea. If anything, it will be the South absorbing the North when North collapses on its own.