According to MacRumors, Apple has tested various storage configurations for the iPhone 15 Pro and iPhone 15 Pro Max devices such as 128GB, 256GB, 512GB, and 1TB.
source https://zeenews.india.com/technology/iphone-15-pro-may-feature-up-to-8gb-ram-1tb-storage-2661331.html
source https://zeenews.india.com/technology/iphone-15-pro-may-feature-up-to-8gb-ram-1tb-storage-2661331.html