AFAIK, technically, that is decided in the design phase of the device conception.

we can see a PC as a long live device because the architecture is heavly backward compatible at the cost of hardware ineficience.

raw power hides that, in a pc that solves the problem

but a mobile device will succumb to new generation hardware because are not enough powerful, its a matter of time

then MER will bring hope to those dessesperated hearts, but we are not talking about that