Actually I think with VR being a focus in the coming generation hitting a 2k/120fps target will be compulsory, at the expense of better visual effects/complexity. But as you said we're kind of at a point of diminishing returns when it comes to graphics, and over the next 15 years or so we'll just be inching our way towards photo-realism and shouldnt expect any dramatic leaps until then.

Also I'm pretty sure the hardware we have currently is capable of much smarter AI, it's just that it's not progressed much in the last decade for various reasons (like cost to implement, "smart" ai not scoring well with game testers bc it may seem frustrating and innaccessible, multiplayer focus etc.). Not sure about this tho I don't really know much about it just remember reading about it awhile ago.

You are right but for one little thing. It all boils down to choices. 

Take the witcher 5 in your example. No matter how big or good a game it is on the PS5. They could make the same game run on the PS4 even if its at 720p with toned down models, textures, geometry, lighting...etc. 

And that will be OK. cause anyone buying the game for the PS4, will know they are in truth buying a PS5 game and that if they wanted to see the game run at its best, then they would have to shell out for the PS5. 

This dilema is by no means a deal breaker. Look at destiny. It also being available on the PS360 didn't stop it from selling a ton on the PS41. 

They could, but the game would likely look and/or run worse than The Witcher 3 does, since it would be so much larger.

On top of that, are developers going to want to make dumbed down versions of their games all gen? I mean, look at games like Shadow of Mordor, or Black Ops III? Sure, those games are on the last gen consoles...but they suffer for it. Could you imagine what The Last of Us, or GTA V would have been like on PS2?

Plus, if devs an publishers already put games on last gen consoles for a period of time...why would it make sense to do it all gen next time around?

I think that is wishful thinking.  I agree that we are in a period of diminishing returns with graphics, but to me that means that Sony will want to totally change the PS5 architecture to make it better.

The original XBox used a PC based architecture, yet you cannot play original XBox titles on the XBox One.

I don't think so. That would be a terrible idea from a business point of view, Sony will actually want to give its costumers a reason to buy a PS5 besides the same games with better graphics. I agree that the system architecture will allow for a smoother transition than ever between generations and probably for backwards compatibility too, that would be smart for Sony because PS4 users will see value on the fact that they would be able to just carry over all of their games to PS5 and Sony would be able to just keep selling their existing PS4 games to new PS5 users or PS5 users who had a PS4 but didn't play some games, all without needing to invest further on re-releasing those games.

I also think Sony will want to push VR as an optional, but crucial feature of the PS5. The first PSVR that comes out later this year already has some pretty nice tech specs (the most important being 120hz refresh rate), so it would be smart if Sony allowed the PS5 to be backwards compatible with it since it's an expensive accessory and people would be pissed off if the were required to buy a newer one. The PSVR could eventually receive a revision specific for the PS5 with a higher resolution and some refinements, but that would be optional, just like buying a newer TV is. Sony could even offer the two versions by the PS5 gen like it does with its headsets.

Totally changing the architecture of the PS5 makes zero sense at all. Absolutely none. There is not a single front that going with a proprietary architecture will be beneficial to Sony or anyone for that matter right now. 

The PS5 will be based on an x86 -64bit architecture just like how the PS4 is. That alone guarantees compatibility with the PS4. Be it BC (which will be easier) or FC. 

Feature wise there will obviously be differences. Mostly due to more advanced fab processes (14nm/10nm which literally means they can cram in 4-6 times more cores on a similarly sized die) but also due advances in memory (HBM which will allow for 500+GB/s mem bandwidth). But what all these translates to is just more of everything. Higher rez textures, more pixels, more geometry (models, npcs...etc)

But everything I just mentioned can still be made to run just fine on the PS4 albeit with less of everything. 

If Sony were to change the architecture and do something like they did with the PS3 (making already hard HD development even harder) then they would have to be the single most stupid company on the planet cause it will mean they just pissed away everything that made the PS4 the developers choice console. 

Yea, not going to happen. The PS5 is going to be a really nice jump from PS4. And the gen will play out exactly like all those before. The previous gen will get supported for about 2 years after the new gen is out, longer with yearly releases, and then support will dry up.

If only they would've given us that choice from the start and not make us waste money on potatoes in the first place.

Yes but Uncharted 4 is still 1080p 30fps

They can always increase polygon count, textures, particles etc. I just think they'll go with maximum visuals before they increase the frame rate because a lot of a consoles sales come from the prettier new experience.

I actually suspected this would happen with the ps4, so I made a thread called ps3.5 xbox540.
It's not a bad idea.
But like some people said, it makes a hard sell to people who already own a ps4