Apple just released iPhone X, but is already working on the next flagship. However, according to KGI analyst Min-Chi Kuo, next year the company will release two smartphones with OLED – displays. His report also states that Apple may return solid stainless steel frames to iPhones to improve data transfer quality.
The steel frame iPhone X is now divided by antenna strips into 4 segments. If Kuo's guess is correct, then the next frame iPhone will look different. As for the two smartphones, it is quite possible that we are talking about a standard-sized flagship and its Plus-modification.
Note that, according to an earlier report from the same analyst, Touch ID will not be returning in 2018. On the contrary, they plan to add Face ID not only to iPhone, but also to a new revision iPad Pro.