If this is true, I wonder if this signals a shift away from the Lightning connector. Apple wouldn't shift to USB-C for just one device. If they do ditch Lightning, that would be one of their shortest-lived standards. But USB-C at least will be more compatible across a range of devices.
Why would it? Assuming the rumor is true, the MacBook Air 12" is a laptop, not an iOS device. We've never had the 30-pin or the Lightning connector on OS X devices.
Or you're confusing Lightning with Thunderbolt which the new USB connector does indeed signal the phasing-out-of, at least in consumer-focused computers.
This.
Was going to write pretty much the same thing. Thunderbolt is in danger of disappearing- I think they may go Display Port over USB-C. It won't be able to do 4-5k external monitors until the next Display Port standard is released (1.4 is it??), but Thunderbolt over Display Port has the same limitation.
Lightning is an exceptionally functional connector and is here to stay for a long time as a versatile & proprietary I/O for iOS devices.