Linux kernel development pretty much reflects what people have and are prepared
to deal with. In time Im sure some drivers will vanish forever as nobody
needs them. In general however once a driver is written it works and carries
on working.
Im using a mix of machines for development including a 5Mb MacII and a 486SX
palmtop I do a fair bit of kernel development on. I suspect this is not
unusual.
Where we will hit driver issues is drivers with few users that are affected
by a major redesign of their subsystem. That should be very rare indeed