This is a good sign for a long lasting peace in Korean Peninsula. I hope it will continue to the goal they want. And maybe the unification of two Korea's just like in Germany.
However, now it is hard to make a prospection what influence this doc really have. Will hope that situation will be changed for the better.
Let's hope for the best (I'm a perpetual optimist) but also stay realistic. NKorea so many times agreed to stop the nuclear program, and broke those agreements just as many times... So, realistically: what's the reason to believe that regime now vs. all the previous times? I mean, I do hope they will stop this craziness, but I wouldn't hold my breath.
As to Iran: they should be hopeful. If NKorea was able to trick trump into meeting them - Iran should be able to pull this off just as well!