It is already here to be honest. I know BrowserStack and other mobile testing platforms (at Facebook and Amazon) do host real devices, both Android and iPhones, in server farms like this. Meta wrote a blog post about it: https://engineering.fb.com/2016/07/13/android/the-mobile-dev...

At one of my previous workplaces, we discussed running the Z3 theorem prover on an iPhone cluster, because they run so much faster on A series processor than a desktop Intel machine.