Verticillium wilt is a systemic disease for which there is no cure. Often plants can grow with the disease for many years before they die, but about all that you can do is to reduce stress on the plant by providing adequate water and fertilizer in the hopes that the plant may ""outgrow"" the disease.
Unfortunately, verticillium wilt is a soil-borne disease, and the spores stay in the soil for many years. So replanting another sumac in the same area is not a good idea. It, too, likely would get infected.