I guess this is a signal for the US to get their nose out of South Korea!
Most probably you are right, they should go out from South korea but all we know they will not leave easily the country.
The U.S. troops lodged on the Korean peninsula are there to support supremacy over China, not North Korea. Besides that, the U.S. is not at all interested in the unification of Korea. Once Korea is unified, the removal of the U.S. troops from the Korean peninsula will be inevitable.