With the introduction of the new 12 inch Retina display MacBook in early 2015, Apple has thrown a curve ball at the future of connectivity on the Macintosh platform. With a new, reversible USB Type-C port, it's likely to initially frustrate then delight computer users.
For backward compatibility with the legacy Mac gadgets we already own, USB-C adapters, gadgets and dongles will be needed to connect external displays and existing USB 2.0 / 3.0 peripherals.
Although quite a few USB-C devices and cables have been released, it will likely take a year or more until Apple revises it's computer lineup completely before we'll see USB-C get much traction. Keep in mind the PC is going to undergo the USB-C transition too, but it will take time.
Eventually the full USB 3.1 SuperSpeed PLUS standard will take data speeds from USB 3.0's current 5Gbps to 10Gbps to rival 1st generation ThunderBolt peripherals. Apple is delivering USB 3.1 REVISION 1 (5Gbps) in it's introduction, but it won't be until REVISION 2 that USB chipsets will be throttled up to the full 10Gbps bandwidth speeds. As such, it's a transition that will occur in stages: The new USB connector first, higher data transfer speeds later. Stay tuned