This generation of consoles is a bit different because of the x86 architecture found in both. Unlike other consoles, we won't see much optimizations as time goes on, because developers already know how to program in x86, and therefore can just about already get squeeze out whatever they can get. x86 architecture is a PC architecture, an older one, but still a PC architecture that's in use today (but not as much). So people and studios developing for the PC or PS4 or Xbox One or whatever are all programming about the same way, so they can all pretty much squeeze out the same amount of performance throughout each platform. I think I explained right? I dunno. It all makes sense in my head, but when I go to type it out, I'm not entirely sure how to properly describe what I'm saying. I hope you understood though.

I do understand that it will definitely be easier to optimize pc ports, but the system architecture isn't the only important thing when it comes to optimization.

It actually is. That's why on the Xbox 360 and PS3 they were able to squeeze out so much power towards the end, because both consoles ran on funky architectures and funky hardware, but towards the, developers were able to understand them and since they started to understand it, they were able to optimize their games more.