Lo and behold, the 2018 iPhones may ship with fast chargers in the box
While Apple's current iPhone 8, 8 Plus and X have fast charging circuitry built in, they ship with regular chargers that take more than two hours to top up an iPhone 8, for example, or three for the iPhone X, as you can see in our testing video above. Apple does offer a fast 29W USB-C Power Adapter that will top off your iPhone to 50% in 30 minutes flat, but that one will cost you $49 extra, and you have to combine it with an "Apple USB-C to Lightning" cable (sold separately for $25).
You can buy a cheaper USB Power Delivery (USB-PD) adapter, but it won't be with the Apple branding, and the whole fast-charging kit will still set you back at least $50. That's one glaring omission when it comes to Apple's iPhones, or may be it's a deliberate strategy, but rumor has it that slow charging will be no more for the 2018 iPhones.
Yep, supply chain sources are tipping that the iPhone 9, Xs and Xs Plus, or whatever Apple names them, will come with 18W USB-PD adapters, as well as USB-C to Lightning cable in the box, not outside of it. This will bring Apple up to speed with current Android handsets, which have been offering fast charging for a while, and the best examples allow you to squeeze a day or two of battery life with less than an hour and a half of fast charging.
source: Chongdiantou (translated)