There’s a long-standing rumor that Apple will ditch the proprietary Lightning connector on the iPhones for USB-C and it seems like 2019 is the year rumors turn into reality.
The latest bit that suggests the move is near is a recovery screen from the iOS 13 Beta that shows a USB-C cable pointing to a computer in place of a Lightning cable pointing to iTunes.
Apple has already moved the iPad Pro over to USB-C as it allows faster charging and access to a heap of accessories (USB-C is a standard of far wider adoption, remember).
It would make sense for the iPhone (at least the 11 and 11 Max, if not the XR successor) to adopt USC-C for the sake of fast charging alone. Keep in mind that Apple makes money selling Lightning to third party accessory makers so it’s unlikely that it will move its entire iPhone lineup over to USB-C.