We have been down this road before, three times this century, 2000, 2007, and now. Each time the North screwed up and cheated. These are great signs, but it is all in the terms and verification. Verification for all of this is key.
The North has to give up its nukes, rejoin the Nuclear Nonproliferation treaty, sign up for intrusive IAEA inspections, and allow intrusive inspections on its missile and conventional weapons. If they balk or do not agree to any of that, deals are off.
I could see where the North and South sign a peace treaty, tensions go down some, the DMZ starts to go away, but things are still tense for years. I could not see the North moving to democracy or even unifying with the South any time soon.