First and foremost it was a political move. It was meant to make Trump look unprecedentedly effective and peace-loving, and it was very successful in that. I was listening to callers on C-SPAN, and it seemed that about 95% of Republicans and 75% of Democrats loved it. It'll help Trump and the Republicans for a long time.

Whether something actually comes of it depends on how serious both sides are going forward. Kim is young, and it is remotely possible that he could've actually been convinced by Trump and his team to undergo a major shift. I'm not sure that it's likely, but it seems possible that Kim has long actually felt trapped in his role, and Trump is offering an attractive way out that he's never seen before. Trump seems to think that this is the case, and if it is, then IMO Trump's actions (even that corny trailer video) could've been very convincing to Kim.

Kim is in a difficult situation. If he gives up his nuclear weapons, then he's quite likely to be Libya'd. (Is he wise enough to know this, though?) But if North Korea continues on its present course, then internal conditions will continue to deteriorate until there is an uprising, or until war breaks out between NK and the US. Despite being Supreme Leader, there are probably also internal political issues preventing him from acting with complete freedom.

Probably, Kim is not really interested in change, and he'll basically just ignore this. Then it depends on whether Trump wants to pursue this issue hard going forward. If Trump makes it his #1 issue, perhaps progress could be made even despite NK resistance.

Most likely, both sides will be content to let it die, perhaps doing several more meaningless agreements in order to make it not look like a failure.

Despite my skepticism, I can't fault Trump on this. The meeting is a small but meaningful improvement in relations; far more than any neocon would do. (For this reason, I suspect that it was mostly set up by Tillerson before he was replaced...)