There is greater reason to believe Kim Jong Un needs to save face than continue to flail against a hardline stance. No less, this is likely in part well born of the consequence that might be the direct tightening the noose around his nuclear proliferation. There is rumor the talks have already actually happened, the agendas already set, objectives finished, but they are going through the motions, see the Olympics, direct talks in the South, and that out of the blue meetings between two heads of state on short notice are unusual, let alone the detonation-in-place that happened at a research site might not have been total accident. Some go so far as a myth about the Forbidden City being a meeting between the states.
Personally I am not buying any of that as truth, but I am certainly going to agree that culturally and on a global political scale, the North Koreans, Kim Jong Un in particular, have no other good options. The difficulty does not arise in some plan that will not effectively do anything or escalate, but keeping the momentum going; if you pull the punch at the end, say after this administration, you lose. In order to legitimize and cement itself North Korea needs to play by newer rules, which it seems to be testing out. As we know it, their regime will not survive if they go down that route without developing cracks and chinks in its armor and perhaps ultimately collapsing. This is the long game, one we have played before with the Soviet Union on a far more grand scale.
The real issue lies in that appeasement has never worked and never will work. This is only a wasted exercise if the defensive posture is ended and the United States backs down, which would be absolutely catastrophic but not out of the realm of possibility for future administrations; the North Koreans will gladly walk right over the United States and without having to fire a single shot.