If you are satisfied with the size of your 14 Pro, then you should know that the 15 Pro is a bit smaller and lighter due to the titanium frame, and most importantly - everything points to the iPhone 16 Pro being larger than the 14 Pro.
The iPhone 15 Pro will immediately support the same AI functions as the upcoming 16 Pro series. 16 Pro will probably be a slightly better camera, better battery (15 Pro already has a good battery), better processor, and new colors. I don't think the 16 Pro series will offer the big news on the hardware, it's all in the software this year.
I would buy a new 15 Pro now. When the 16 Pro arrives, you can see if it's worth it, and then you can sell your 15 Pro as almost new - or keep it until the iPhone 17 series, as according to the rumors, comes with the real news (iPhone 17 Slim?)