At that focal length, stabilization might not be
needed, per se. However, surely it is not a bad thing to have one. I assume that's why Leica decided to include stabilization with the Q3.
I've always thought that 1/focal length rule is overly optimistic. A decade ago, with my first camera (Nikon D750) I conducted a simple test with an unstabilized 35 mm lens by taking pictures of a newspaper at its minimum focus distance, and I concluded that I could only be sure that my pictures are consistently sharp if I take pictures at 1/(4 * focal length) second, i.e., 1/140 s or faster with the 35mm lens. With my IBIS-equipped Sony camera, I finally feel that it's okay to take pictures at 1/focal length second.
Yes I assume that Fuji engineers made the decision not to include stabilization to ensure that the overall size of the camera remain compact. I have no qualm about that, and I'm sure the camera will be a very good choice in a lot of shooting scenarios.
I agree that high-megapixel cameras are surely not needed for people who don't print, or print at small sizes like I do. However, I'd like to point out that another benefit of high-resolution cameras is that they reduce aliasing. We can see this in action when comparing the GFX50S and the GFX100S (ref:
dpreview.com)