According to many iPhone prognosticators, Apple will release a triple-lens iPhone in 2019.  Sources of the prediction include Mac Rumors, BGR, and AppleInsider.

Depending on whom you believe, the triple-lens system will give the iPhone a high-quality 3x zoom, or will improve the quality images taken in low-light conditions.

The mock-up of the triple-lens iPhones was created by Martin Hajek and was published in iDrop News.