Yes, South Korea should be allowed to become a world power, because South Korea being more powerful would help aid in the destruction of North Korea. North Korea would crumble under the pressure of having a super power to its south. This would be a good thing for human rights in North Korea.
If South Korea is open to free trade with the rest of the world, and, if it has the capabilities to do so, it should be able to become a world power. A country's ability to become a world power should not be determined from other countries but by its goods exported.