https://www.theverge.com/2017/9/12/16298006/apple-iphone-9-naming-why

Apple just announced its iPhone X. It’s the new flagship iPhone that will be released in November, weeks after the iPhone 8 and iPhone 8 Plus go on sale on September 23rd. Apple says you’re supposed to pronounce the iPhone X as “iPhone ten,” and it’s designed to mark 10 years of the iPhone. While the iPhone 8 is an iPhone 7S in all but name, the number jump across all the new iPhone models means we’re now officially missing an iPhone 9.

Apple’s typical S naming is gone for this year at least, which isn’t entirely surprising. Samsung launched its Galaxy S8 earlier this year, and the company’s Note 8 will be available on September 15th (the same day iPhone 8 preorders begin). Going up against the Samsung Galaxy S8 and Galaxy Note 8 with an iPhone 7S and iPhone 7S Plus doesn’t really make as much sense this time around. Instead, Apple appears to be using a great marketing trick for this year’s iPhones.