In my view, N. Korea is not bluffing. She will have nukes if the current regime continues in N. Korea. She may pretend that she is further along than she actually is, in order to gain some advantage at the negotiation table. Or she may pretend that she stopped working on nukes for the same reason. However, either way, she will get them eventually.
I don't think NK is totally bluffing either. But I doubt they can deliver a nuke on a longdong even to Guam. A nuke is one thing, one that fits on an accurate long range missile is another.