Given the latest iPads having USB-C, as long as Apple (a) works with the MFi accessory vendors well in advance of release of a new iPhone, and (b) comes up with a compact male USB-C to female Lightning adaptor (to avoid obsoleting existing accessories...and such a gadget would also let people use Lightning earphones/headphones with a Mac), IMO having USB-C on all iDevices as well as Macs would be a huge improvement, both toward standards, and to increase the market for quality USB-C cables and bring down the price. Not to mention the possibility of 3rd party accessories (such as external stereo input or DACs) with cross-platform support.
With those prerequisites, IMO the USB-C connector is compact enough that there's no excuse NOT to make that change.