Yes. The DMZ should remain just as is; even after the reunification of the North and South Korea. The DMZ has been a place where wild life is protected, and it should not be changed due to reunification. The newly unified country will be able to enjoy the wild life together.
After the reunification, the DMZ should not remain an ecological reserve. One reason for this is that it would continue to be a barrier between North and South Korea and could add to tensions between them. Another reason is that it has been a place that animals cannot live because of the danger. There is a park in an isolated area of the DMZ that contains endangered species and many kinds of animals and I think it would be good to keep that, but not the entire DMZ as an ecological reserve.