1. Artists that use SD etc., will save a lot of time and have a big edge. Example: Generating references instead of searching for them, Generate random inspiration(s) for abstract ideas, Variations of a particular idea to compare and contrast.
2. Non artists who have powerful imagination but lack the artistic skill will stand to benefit as well. For example, I look forward to generating visual companions for my poetry, essays or fiction. I have the choice of commissioning an artist if my piece is successful.
3. Artists that are purists and masters of their craft with a very unique style will continue to thrive in their niche. These people have to lobby and come up with a license that explicitly prohibits feeding their images for learning. But a skilled artist can replicate the style and feed it. There is an ethical line here that may require creative tweaks to existing laws to protect people that fall in this category.
Super exciting tech and I can't wait for this to move over to 3D models. I know 2D image to 3D model is already pretty close to being real(nvidia ominiverse, nerf etc) and SD can be the starting point of that pipeline. Prompt -> 3D world that can be decomposed to meshes, textures and USD will change the game development landscape quite a bit.