https://www.cnbc.com/2017/11/13/iphone-x-plus-said-to-launch-with-two-other-iphones-in-2018.html

Apple will reportedly launch three new iPhones in 2018, including a brand new high-end flagship called the iPhone X Plus with a large 6.5-inch display, according to a note from KGI Securities analyst Ming-Chi Kuo obtained by MacRumors.

That would be the largest display Apple has ever included in an iPhone.