That would be the largest iPhone display ever. The has a 5.8-inch screen and the iPhone 8 Plus has a 5.5-inch display.
Kuo said the 6.5-inch version and a new 5.8-inch model will use OLED screen technology that's similar to what's in the iPhone X. The OLED panel is one reason the iPhone X is more expensive than the iPhone 8 and iPhone 8 Plus. To hit a more affordable price point, Apple will launch a 6.1-inch model with a more traditional LCD display, he said.
"We believe the major hardware difference in the two new OLED models is size, in a bid to satisfy various needs of the high-end market," Kuo said. All three phones are expected to feature a full-screen design and 3-D sensing, Kuo said, suggesting that Face ID will replace the home button entirely in 2018.
Apple was not immediately available to comment.
Read the full report at MacRumors.
Correction: This story was revised to correct the source of the name iPhone X Plus. It was speculation from MacRumors.