while i think that trump is probably right in deducing that promoting peace will make him more popular than beating the drums of war, i don't imagine that an american pullout from south korea is at all imminent.
see, here's the thing: when it was about war it was smoke & mirrors. and, when it's about peace, it will be smoke & mirrors, too.
i could be wrong; maybe, i missed something. but, the situation in korea is really pretty intractable. and, it would require a major shift in thinking from one or both sides to break through it.
that said, you don't need a peace agreement to increase trade, and that's what everybody should really be concerning itself with.