I would be optimistic.
There won't be a revolution in North Korea - the State has too much of a hold on its people. Society is so atomized, so broken down that no one trusts anyone, and no one will dare form a revolutionary movement because no one can talk to anyone in order to get one going. The only people who could turn things around for North Korea have NOTHING to gain and EVERYTHING to lose by doing so - their own people hate them so much, that any attempt to slacken the hold of the people will cause them to revolt, so they wisely (for them) will never loosen the screws.
If the North Koreans could have ever overthrown their regime, they would have done it around the time they started dying en-mass from starvation. North Korea is a grim reminder that with enough will and enough force, a state can ALWAYS oppress its people, indefinitely, forever.
We could wait for a couple more decades and hope that whoever replaces Kim Jong Un will be nice enough to open up North Korea (and subsequently lose all power and maybe his or her life), or we can hope that a military strike will topple it. If you knew exactly how awful life was in North Korea, you'd want it to end tomorrow. It's literally like 1984 come to life - the only thing missing is the televisions that watch you, and that's only missing because they lack the resources to develop it.
North Korea, if invaded, would not turn into Iraq. It's an isolated nation that terrorists can't infiltrate, unlike Iraq. And no terrorist would want to go there anyway. It doesn't have any ethnic tensions - the South Koreans are the same. The North Korean citizens have no love for their own nation -they keep trying to escape after all. They are relatively well-educated (the one thing North Korea has managed to be somewhat capable of doing, but even that is falling apart) and would probably integrate into South Korea.
It's not Iraq. It's an entirely different situation to Iraq and Afghanistan. It wouldn't play out the same at all.
Having said that, I am aware of the dangers of invading the North - they have nukes. Primitive nukes, but nukes none-the-less. They have a ton of artillery pointed directly at Seoul, which is quite close to the border. Without a doubt, they could kill a LOT of South Koreans. It would be the very last thing they'd ever get to do, because they would quickly find themselves non-existent after the act, but it is something they could do. Also, reintegrating an entire nation of starved, terrified and oppressed people who have no working knowledge of 21st century life into South Korea might very well bankrupt that nation entirely.
But when you at the horror of North Korea, I would say it's worth it. North Korea is the second worst government I've ever read about - the only one which is worse was the Khmer Rouge, and not by much. They make mothers drown their own babies in buckets because they THINK the father is Chinese! Did you read what I just said? They MAKE MOTHERS DROWN THEIR BABIES. They sentence three generations of a family to prison camp for the crime of ONE PERSON! They selectively starve entire regions based on some perceived lack of loyalty! They'll kill you if a smudge of dirt gets onto a portrait of their "dear" leader! It's like Orwell's 1984 - it REALLY is. It's that book come to life!