Secondly, I don't know the whole opinions of the rest of the world but for the stakeholders like China, Japan and the U.S., I don't think they really want us to reunite. Korea has played a role of a bulwark for superpowers. For the U.S. and the Soviet Union in the beginning, and now China took the position of the Soviet Union. After the unification they will lose their influence on Korea. And Japan will hate its rival (industrially and historically) gaining huge resource for future advancement. I mean, no one can exactly predict the results and effects of the unification. Your opinion about the intentions of other countries' heads seems too naive for me.
To sum up, most of us want to achieve the unification as long as we carefully plan it so as to minimize the financial burden. Probably almost all Koreans agree that the unification will make the country much more powerful in the long run though it'll deteriorate the economy in the early years. However, I don't find we can achieve it in this century because of diplomatic reasons as well as internal ones. Too many world powers are related to it so it's an extremely hard problem to solve. I consider it one of the open problems in diplomacy like the ones in math.