It looks like the iPhone Pro and Pro Max sizes will get a bump upwards, and potentially one or two new color options. I suspect they will look a LOT like the iPhone 15 line in appearance, but the biggest changes will be in the new software: iOS 18.
That said, Apple is offering
bumped-up trade-in credit for your old (pre-13) iPhone(s), so there are some potential good deals on iPhone 15s at the moment if you want to deal with Apple directly.
It's also a good time to consider a new phone + plan. Freedom Mobile has some good options, and they are driving the other companies to offer similar deals. Win/Win!