2017 will see the release of three new iPhones; the all new iPhone 8, as well as the refined iPhone 7s and 7s Plus. Since the release of the iPhone 3, Apple have followed a more or less predictable pattern of releasing a new model, and then the 's' version the following year. This year, however, the iPhone 7s and 8 will be released, with the iPhone 8 offering users a complete redesign of the iPhone, featuring an 'all-screen' design with no home button, as well as a fingerprint sensor built in under the screen. On the other side, the iPhone 7s will be a more predictable upgrade on the iPhone 7, more in line with what we expect from an 's' version of the iPhone.
In terms of features from the iPhone 8 that won't be available on iPhone 7s, one of the most useful features that will be missed is wireless charging. This is because the iPhone 7s will continue use the aluminium, unibody housing of the iPhone 7, rather than the glass constructed iPhone 7 which will allow wireless charging.
Outside of this, it looks like these iPhones will hit the market in September of this year, so over the coming months some of the confirmed features will be stated, or leaked as the case may be.