[squarefoot]

"I think incidents like these are a pretty solid argument for incorporating overvoltage protection into 5V USB peripherals."

Agreed, though for some peripherals effective overvoltage protection that goes up to the maximum port output could cost more than the device itself. I would rather get the chance and redesign the connector so that there won't be any risks of exposing old devices to higher voltages, then introduce it slowly to new laptops (say one port this year, two the next two years, etc) and possibly provide small external adapters that fit on the new connector on one side and export the old one (maybe more if working as hubs) with adapted voltages for both signals and supply lines. To me having multiple voltages driven by software on the same connector where one could insert devices that can't protect themselves in case of failure is asking for troubles. One day someone will connect a cheap LiPo charger to one of these ports and if the port firmware flips nasty things can happen.