The same thing that has previously happened with discontinued Intel Macs or PC hardware that is no longer supported by Windows.

You can still boot Linux natively on it.

i have no idea how you think apple silicon will discontinue support for itself.

the hypervisor framework documentation, that i linked above, is pretty clear; the linux builds for arm run extremely fast on apple silicon because hypervisor framework gives them hardware access, in some subsystems directly (memory mapping for example), in other systems through a shim (graphics hardware).