I fear that an invasion is inevitable at some point, but what will be the trigger?
1. NK destroying a manned jet or boat in international airspace/waters
2. One of their bombs accidentally landing in a neighboring country e.g. Japan
3. A deliberate non-nuclear bomb sent to the US, but shot out of the sky before it reaches them.
...
Launching a nuclear bomb at the US?
Realistically it's hard to imagine any of these scenarios playing out as they'd certainly result in the beginning of the end of KJU's reign (plus the deaths of millions of people). The whole reason he's probably been hell-bent on nuclear technology was to deter the US from his country given all the "regime change" they've been dabbling in lately.
China will always find a way to trade with NK even if it isn't necessarily out in the open. The very last thing they'd want is a US influenced unified Korea on their border.