Re. the PPC era and whether it will be like that in the future, this is from a lowly web backend developers perspective, so I might be naive, but hopefully we've learned to build generic solutions without sacrificing performance, when it comes to things like this, and it doesn't devolve into a code that only runs on X-hardware type thing.

I think it's a more common problem to see things like the T2 security chip not being present on older hardware or hackintosh(unsupported) hardware, so if you're not running the right hardware you can't take advantage of a feature (AR in certain iPhones) or you won't have the performance advantage (Filevault encryption with T2 chips vs encrypted by CPU).