If the S3 sells according to Leica's expectations, it will be because of what it is, not in spite of it. It will be because it is an SLR camera with an optical viewfinder, still able to capture fantastic photos. Look at the very positive initial reviews of the Nikon D780.
Cameras like the GFX 100 and the X1D can do so many things that the question arises what the aims with the cameras are, what the aims of photography are. I don't take better photography because the camera is smaller, although that can be convenient sometimes, and I don't take better photos if the camera can also do 6K video and has a built-in can opener. After 10 years with electronic viewfinders, I still prefer the optical ones.
The S3 won't be a GFX 100, and it doesn't need to be. It needs to be better than the S2, enough better to be a tempting upgrade for those who use that camera as a tool. It needs to be a dagger for those who don't wan't a Swiss Army Knife.