When there is a USB-D (if ever), then the USB standards body would push for that adoption and I'm sure the various hardware companies would follow along. Maybe Apple would stay out again but who knows. The regulation doesn't need to be static 10 years from now.
USB-IF is largely made up of the major hardware companies.
You have far more optimistic faith that companies would push for legislation that causes themselves changeover costs - with no competitive advantage benefit - than I do. Foxes guarding the chicken coop if you will. Tendency is to maintain status quo - particularly once they've successfully eliminated the possibility for one of the companies to get a competitive jump on the others with a new connector type.
You also have a far more optimistic view of how quickly standards and legislative bodies move. It took USB-IF twelve years to finally (maybe) fix the hot mess they made of USB3 branding. Imagine if they then had to push through legislation for it to reach consumers?