48v made sense years ago, the only reason we haven't done it is inertia. You're spot-on; the PSU is not making voltages that're directly used by components anymore, with the possible exception of 5v for USB and stuff. Everything else has a local DC-DC converter and the "12-ish" is used as an intermediate distribution standard.
Pursuant to that, the ATX12VO standard is a huge step in the right direction. It ditches the 5v and 3v3 rails from the PSU and uses 12 only. This requires only modest changes to peripherals, most of which were getting most of their power from the 12v rail already.
I think it's an excellent stepping stone on the way to an ATX48VO or something. That will require some more changes because a lot of popular power semiconductors are only rated to 30v or 35v or something, so there will be some push for a 24v compromise, but I think the efficiency gains with a higher voltage will ultimately win out.
Pursuant to that, the ATX12VO standard is a huge step in the right direction. It ditches the 5v and 3v3 rails from the PSU and uses 12 only. This requires only modest changes to peripherals, most of which were getting most of their power from the 12v rail already.
I think it's an excellent stepping stone on the way to an ATX48VO or something. That will require some more changes because a lot of popular power semiconductors are only rated to 30v or 35v or something, so there will be some push for a 24v compromise, but I think the efficiency gains with a higher voltage will ultimately win out.