Code discovered from the tvOS source confirms that Apple will have the A17 chip on the iPhone 15 Pro.
Apple added identifiers and references to ‘iPhone 15,4, iPhone 15,5, iPhone 16,1, and iPhone 16,2 in the first tvOS 17 beta before removing them quickly in the fifth beta version. The numbering system coincides with the release of the A17 3nm processor and the A16 processor for the iPhone 15 Pro Max and Pro, and the iPhone 15 Plus and iPhone 15, respectively.
The sequences 15,4 and 15,5 are the same as the iPhone 14 Pro Max and iPhone 14 Pro, which uses the ‘15’ as a placeholder for the A16 chip. Code enthusiast @aaronp13 put up a post on Twitter to announce the news, and it’s the same person to have found the code that revealed the iPhone placeholders 14,1 and 14,9 will have the A15 chip.