In talking about a switch to USB-C, one point seems to be missing - Lightning gives Apple absolute control over which devices can connect. If you don't pay up your MFI fees, and get your device blessed, then there's a chance it can be blocked in a later firmware update, at Apple's discretion. This extends all the way down to charging cables, (tho I'm not sure how well it's enforced / easily sidestepped for charging cables).

Maintaining that level of control, and maintaining the licencing revenue stream, over USB-C, might prove difficult?

Either that, or they change the connector, and leave all the handshake protocol / custom chipset at both ends in place, in which case we will end up with devices that are USB-C in connector only.