Agree. I wouldn't buy anything that didn't include USB-C. I know that if I start getting my connectors/dongles now they'll be around for awhile. Plus, for me I don't really use them that much. They pretty much stay docked to my LG 4K display and I really only use them for charging my various iOS/watchOS devices.A very personal decision.
If the 2015 works for you, keep it.