The next and final expansion for The Witcher 3, Blood and Wine "is a graphics upgrade from the base game".
In an interview with Eurogamer, senior environment artist Len de Gracia explained that Blood and Wine uses new display methods and optimisations to look better than the core experience. "We just wanted to show that we can actually push it to the limit this time," he said.
It’s partly because its setting, Toussaint is an entirely separate map. As de Gracia puts it, "it’s like a fresh development. Blood and Wine we literally started from scratch."
Source: IGN Video Games