Well, with so much effort to isolate North Korea and bring them on the path of war with repeated threat, I would not expect less from them.
And knowing the past history of the USA in deescalating conflict, I would expect war at some point.
You don't see anything wrong with a madman in a country always on the edge of collapse that's constantly threatening to turn the USA into a crater having nuclear weapons?
Kimmy is over there threatening to bomb out the US and Japan and put everyone's heads on pikes pretty much weekly. I don't recall even our crazy fucker president Trump saying anything remotely close to that.
Submarine launch is harder and the warheads must be smaller, but ICMB's are already considered unstoppable so it doesn't matter.
Prevailing wisdom seems to be that Kim treats nuclear weapons as an important deterrent from invasion, not a first-strike weapon. The US doesn't have much appetite for invasions atm, so the chances the missiles will ever be fired is pretty remote even if he does have them.