OP makes some incorrect assumptions. USB A to USB C will be the most common, by far, just like USB A to Lightning. You get different cables, not different cases. Laptops will eventually adopt C ports for the ability to charge themselves through it but they will still have USB A too (duh).
Actually, the majority are going to be A to C cables. C to C is mostly a "mobile to mobile" or charging option, like USB OTG for microUSB 2.0 B. I wouldn't mind seeing it on laptops and desktops, but they will still have A ports for USB1.1/2.0 in addition to that and A to C will still be the standard cable for most devices. Obviously, phones and tablets will adopt it fully. Laptops that charge through it will be next.
I have had my Galaxy Note 3 since launch and I greatly appreciate the microUSB 3.0 B connector's reverse compatability with microUSB 2.0 B cables. It was not yet time to ditch that connector, but I would still prefer something reversible that will not damage the device with unexpected force. It's like Apple's Lightning combined with MagSafe. Notice: Lightning still has a USB A side.
Apple violated this standard with the microUSB to Lightning adapter.