Have you ever sat in bed with a MacBook on your lap and the power outlet is on your right? Meaning the MagSafe cable has to go one round around your laptop. Or have the projector cable on the left, so your cable has to go another round.
With USB C, there is no such thing as a wrong port. I can plug in a cable or adaptor on the left or right side of the laptop depending on which side is more convenient for me.
The USB C is so sleek and slim and reversible and just so much better-design than the existing ports today.
I can't predict the future, but I do believe that the best way to predict the future is to create it yourself, and I want to believe in an all usb-C future. My MacBook Air is still going strong, but when it is time to upgrade, I have my sights set on the 13" touchbar MBP, and all my accessories will be USB C. That much I can assure you.