Iran and North Korea are countries that are struggling with their economy. Countries that are economically weak should be the last countries to pitch tent with China. But they would, out of sheer necessity and obligation to China, as long as their current leaders continue in power.

Iran is already ripe for a regime change as its citizenry is getting agitated with their current economic predicament and is rising up with civil disobedience.

As for North Korea everything is under wrap. Nobody knows what is happening on the ground as their state controlled media dishes out only skewed news in favor of the regime. Your guess will be as good as mine.

These countries have nuclear capabilities but would be extremely careful to deploy them because doing so would be mutually destructive. In such a scenario, they have more to lose than the other nuclear armed countries which are economically far better off or less dependent on other countries than these three countries.

You left out Pakistan. They are in no better position than Iran.