Sure, but having already invested goodwill and money in Lighting, the benefits of switching to USB-C would have to be substantial before it makes sense for Apple to do so. To reality is that for most of Apple's users, USB-C offers no discernible advantage and quite a few disadvantages (having to buy new cables and peripherals again).
Well, besides being able to charge your phone from your laptop charger, use the same USB flash drive in your phone and laptop without an adapter, use the same powered noise-cancelling headphones in your laptop and phone, connect your phone to your projector/monitor/TV using the same adapter as the laptop, and so many more.
So, there are some benefits if you already have other devices that use USB-C. Most people don't however. Not yet. What people do have, is tons of crap that is Lighting compatible.
