Apple will release new iPhones in 2019. This hasn't been confirmed by the company, but it's released a new iPhone every year since it came out. The launch is typically in September.
According to Ming-Chi Kuo, an analyst for TF International Securities with a track record of correctly predicting upcoming products, Apple looks poised to release three new phones with the same screen sizes and bodies as the current models.
They're expected to have updated processors, potentially a triple-lens camera on the back, and a new kind of sensor that would allow the rear camera to sense how far it is away from walls and other objects.