According to a new report from Bloomberg's Mark Gurman, Apple will most likely replace the iPhone 14 Pro Max model name with the iPhone 15 Ultra name.
Apple started using it's "Pro" naming in the iPhone with the iPhone 11 to differentiate the regular budget end iPhone models with the high end "Pro" lineup.
With Apple recently making its most powerful products with the "Ultra" name like M1 Ultra and Apple Watch Ultra it is possible that we can get an iPhone Ultra.