I mean sure, but that means they would have their necks out in the open for a protracted period of time, depending on how the negotiations pan out. So South Korea would stand next to two countries that are expressly not allied to it and depending on for negotiations to go their way without any kind of leverage. Reunification certainly isn't desired as an overnight thing (would be disastrous on SK economy, East Germany but so much worse), but there is also the matter of there being two separate ruling elites at the moment. One will have to go away in the future and Kim is always walking a fine line in regard of maintaining his grip on power although it doesn't look like that on the outside. A lot more twists and turns can occur here.