According to a report from Japanese blog, Mac Otakara, Apple will include their 18W USB-C Power Adapter in the 2019 iPhones’ box. It is the same adapter included with the 2018 iPad Pro. The 2019 iPhones will also include a USB-C to Lightning Cable.
If Apple includes this, the fast-charging feature will finally be available without having to purchase the Lightning to USB-C cable and the 18W Power Adapter for $48 from Apple. Fast-charging has been a feature on the iPhone since the iPhone X, iPhone 8 and iPhone 8 Plus.