North and South Korea: a permanent détente?

In a remarkable scene last week, the South Korean Unification Minister and the head of a North Korean delegation walked, side by side, into a meeting in the Panmunjom peace village in the Demilitarized Zone.
Pyongyang has already said it'll send a team to the Winter Olympics in the south, and there's talk of resuming family reunification and increasing military confidence.
But is it all temporary, or is a more seismic change afoot?