The DPRK is one of the most unstable nations in the world (next to Iran), and when Kim Jong-Il died last december, the BBC actually said that it became "more unstable", and back in January, the brother of Kim Jong-Un(stable)
said that North Korea will most likely collapse
China doesn't want the division of Korea to be permanent (and to be fair, neither does anyone else for that matter), but one thing is for certain, when the DPRK collapses, South Korea will most likely automatically take over the entire peninsula, along with the Korean People's Army being absorbed by the ROK Army (South Korea's army), like East Germany's National People's Army was absorbed and merged by West Germany's army, and would make it the 4th largest military in the world, and a unified Korean military would have the largest number of reservists as well as one of the largest numbers of military hackers. Plus, if North Korea collapsed, it would be a good thing because the North Koreans would be living under a government that really cared about them (South Korea's government of course).
North Korea's economy is currently worse than that of East Germany in 1990 when German reunification happened, while South Korea has not only the 15th largest economy in the world, but the South Korean capital of Seoul is a major global city and the second largest city in the world (following Tokyo, Japan), consistently placed among the world's top ten financial and commercial cities alongside New York and Tokyo, and is the home city of Samsung, LG, and Hyundai.
As for culture, though traditional Korean culture and history are shared between the two halves, the modern cultures of the two halves have separated following partition, unlike German reunification, in which the 41-year-long separation has left significant impacts on German culture and society even after two decades, the extreme differences of North and South Korean culture and lifestyle will likely last even longer than that of East/West Germany, having been separated for 65 years.
Lately, there have been several apparent signs of reformation in the DPRK, one being that
a pair of statues in Pyongyang of Lenin and Marx were torn down, and then we have the Ryugyeong Hotel in all it's glory, which would cause a large surge in tourism for the worlds least visited country, and
cell phones are becoming popular there as well, among other things.