I'd say that HDMI would be make the machine a lot more versatile than USB-C (or MiniDP, for that matter). Showing a few photos on a TV, using your client's projector for an unplanned demo, using an absent coworker's screen - I can't remember how often I've envied MacBook Pro Retina users for that port. It's magic.

TVs and projects are not going to switch from HDMI to USB-C either, so waiting won't solve that problem.