Maybe not soon but it is coming.
My reasoning is that many like to point out that NK has made threats like this throughout its history, I counter that by pointing out Kim Jung I'll made threats, we have no historical basis to compare these threats with Kim Jung Un. Not to mention that I have a lot of friends in the military from when I was in. About once a week another one is getting sent there, were building up our forces on the ground...
Not to mention that NK doesn't have to use nukes to make a huge mess in SK. Their conventional weapons, like artillery, can cause severe damage to US and SK forces while their army invades. That army has more numbers than US and SK forces over there.
Don't get me wrong, I feel we'd win the war in the end but it got the potential to happen and it will be a long fight.
Also, what if we in the US or SK decide to do a preemptive strike, that would force the norths hand. If Kim Jung Un is trying to consolidate his military power, he can't ignore that, regardless of his intentions now.