So Apple introduced the 12" USB-C Retina MacBook earlier in 2015. Then announced the next-gen AppleTV with a (largely ignored) USB Type-C diagnostic/service port on the back of it. More recently, new Retina iMacs were released with all sorts of under the hood improvements, but a USB 3.1 Type-C interface isn't one of them.
Guess we'll have to wait awhile longer. Not sure if we'll see any USB-C Mac revisions prior to the Holiday shopping season -- Or if Apple will wait till early in 2016 to tackle the USB 3.1 transition in earnest.