

The material conditions of the world would have to be so different from what they currently are in order for this to happen, so it’s hard to speculate. Tensions currently are slightly increasing between ROK and US (it seems) but the ROK bourgeoisie would certainly not willingly give up their class position, and I’m sure that the US would go to bat for them if push came to shove. So I don’t think it would be able to happen until the US’s influence at the world stage diminishes sharply. Currently it seems to be on the decline but obviously still very relevant.
My prediction of how it would ultimately happen would be that the proles in ROK would gain more class consciousness as a result of labour struggles, and the labour movement would get powerful enough to threaten revolution, in which case a post-recolution society could consider/discuss reunification.
I think the current free travel status is very much dependent on the US’s role in geopolitics, so if that sharply declining is a precondition for reunification, I think that it would be a much different situation than it is now.
I can deal with the sideways ones but the trains in my city have backwards seats :(