I think you're seeing that in too much of a unilateral sense. Kim's overtures are to the world. If he backstabs the current peace process he's not just messing with Trump, he's messing with South Korea, China, Russia and the EU. Basically anyone who got on board and trusted him is who he'd be backstabbing. You're thinking in too much of a USA-centric view.
Sure, the USA will have a new President in a few years and maybe another chance for Kim to "play nice" if he somehow does a 180 and starts pumping out nukes and going all beligerent again, but that doesn't change the rest of the world. Frankly, that scenario doesn't make a lick of sense, either. If Kim goes back nuclear, it needs to be end-game worthy bullshit, and they don't have the capacity to pull that off. That's why he was hoping to just make a nuke and be able to mothball it and use it as propaganda and a bargaining chip. Firing the nuke would have been the last thing he'd want to do, because deterrents don't work if you shot first. Whatever he plans to do with a hypothetical nuke, the goal is that North Korea and its leaders survive. Firing the nuke at America would basically be guaranteed instant death, which is the opposite of North Korea's goals. So, despite how panicky everyone gets we can completely rule out the possibility that North Korea will fire a nuke at America. They are not the USSR, who would have been theoretically capable of withstanding a nuclear war on equal footing with the USA.