Renting out compute is a viable business model. That's part of what the big and the small cloud providers do. It's just (on its own) not a "get rich quick" business model anymore.

Why would it be any different for inference? If we believe OP, it'll just become part of regular compute infra, and thus part of the renting-out-compute business model.

I think it's an open question if the current generation of inference investment will pan out, but in the long term, there'll be a balance between investment cost and margin, just as in every other industry.