I would agree that it's unlikely that Google or Microsoft will start making prosthetics -- although they could spin GCP or Azure off into other corporate entities or operators who did someday.

More likely would be that Google, Amazon, Microsoft and some affiliated company would be competing in a space where telemetry from something like a prosthetic was reporting information that had some value.

In any situation, the downside of renting something is that you lose control. It is something that you need to think about and incorporate into your business strategy in some scenarios.