Rick, the scuttlebutt I've heard says that the relay (and more important, switch contacts) simply *cannot* be met in a reasonably cost effective and reliable manner.
That may be totally wrong, but in theory 42VDC systems and electric
direct drives (i.e. for power steering) were going to be deployed by now--and something has prevented that from happening, with no official comment from the many sources that said we'd be on 42VDC systems by now.
Could just be they've decided not to make any changes until they are most economically phased in, i.e. by major platform changes like GM's "skate" with a complete new engine
and power system. (Why waste money
upgrading systems you're looking to scrap?<G>)
Since the only reason we have a 12VDC spec in cars and trucks today is the US Navy
...I don't see any incentive for carmakers to make a similar change.