Not sure if the scope of the game has changed, but CDPR have stated in the past that this game is bigger in size than Witcher 3. And each of the districts will be distinct and different.
I don’t imagine you’ll get bored.
I think they stated that the map is smaller then Witcher 3 but it's more dense...it's not about getting bored but a bit more variety would have been nice...I go back to the Arkham City/Knight example...I never got bored in those games