I think most people suspect this is the eventual scenario.

Trump faces major opposition for challenging North Korea now while they currently only possess a few nukes possibly capable of reaching our west coast. Imagine how much greater the opposition will be against challenging North Korea once they've developed dozens of nukes capable of hitting any city in the US as well as those of our other allies around world.

The question then will be:
Are we willing to risk losing hundreds of millions of lives in a nuclear war just to prevent 50 million South Koreans from falling under communist rule, most of whom would likely also be killed in that nuclear war anyways? Not to mention what other global rivals might try elsewhere if the US were crippled by a nuclear war with just North Korea.

We pulled out of Vietnam and the world continued on. It's a pretty safe bet we'd pull out of Korea too under those given circumstances.