They will never call it the iphone pro. Nothing about it is pro. The iPad pro has a better screen, faster processor etc. The Macbook pro has a faster processor etc. The iPhone 8 only has a better/different screen and a different auth method and perhaps a slightly better camera. Pro has been used to denote a device that is for pro users. More powerful and features for professionals. The 8 will have none of those.
I reckon it will be a new name that doesn't bear any relation to the current names of other apple products and won't mess with or lock apple into any naming convention for next year. They will probably return to iPhone 8/+ next year where both will be based on the new notch design so making the name generic would be sensible.
Lol, the iPad Pro has a better screen, faster processor, the MacBook Pro has a faster processor. The OLED iPhone will have a better screen, faster processor, seamless facial authentication, better camera, etc. But can't be called Pro.
Listen, I get it. None of us know what it will be called. But really can't rule out anything. Except for iPhone Banana. Or maybe not. iPhone Banana has a nice ring to it.