The big increase next-gen is going to come from the CPU imo, GPU I only expect about 12TF for PS5 atm, and the ram increase is certainly not going to be equivelent to the past, 32gb tops imo.

This is what I keep saying. People keep talking about 10TFLOPS and 16GB of RAM like it is going to be something that makes for an amazing PS5. This is Gamecube to Wii levels of console to console performance. As you said, this would just end up being a super high fidelity PS4, because devs would not have the gains to do anything other than make 4K/30FPS versions of PS4 titles with improved textures.

This may end up happening, but I just don't think doing a half generational update and calling it PS5 is a wise decision. People have been conditioned to expect a certain level of performance increase from numbered PlayStations, and I think doing a PS5  that is only half the leap we have seen in the past could do major damage to the PlayStation brand. To me, it would be much wiser to call it a PS4 Premium, and not try to build hype around something that can not live up to that hype.

Keeping the ps4 name means the other PS4 models would need to still be supported. If you dubbed the new device "PS4 Premium" when it has a different CPU and GPU... 

Pro uses the same GPU (just has the chipset mirrored and runs at a higher clock), it uses the same CPU just overclocked, and it still has 8gb GDDR5 (just with higher memory bandwidth and an extra gig of DDR3 for the OS). Pro IS a PS4.

Changes beyond what the Pro does makes for an entirely new machine, not a ps4, which would just make things a massive pain in the ass.

That is the thing. It should still be the PS4 CPU and GPU, just like the Pro still uses the same CPU/GPU, with minor new features. At 7nm they should be able to get the PS4 CPU running at 3GHz and the GPU should be able to do 10 - 12TFLOPs by having 4 identical GPUs as opposed to 2, and running at around 1.2GHz. Give devs 16GB GDDR to play with and keep the 1GB for Multitasking, or maybe bump it up to 2GB with additional multi-tasking feautres for Premium users. This would be a $399.99 console in 2020. 

This would be extreamly easy for devs to build to, and give us full 4K/30fps and 4K/60fps versions of PS4 games with no frame rate and pacing issues. It is as good as we are going to get from a device in 2019 - 2020 at the $399.99 to $499.99 console pricing, whether it is a fully new architecture or a modified PS4 APU. 

For games that are not possible on PS4, we need a true generational leap. 8 Core CPU with Multi-threading or Two 8 core CPU's side by side like the PS4 and XBOs Two 4 cores side by side. Either way it needs to be much more powerful per core than the current PS4 CPU. We need 20+ TFLOP GPUs, and a Minumum of 64GB of RAM dedicated to games, with at least 8GB for the OS, but 128GB would be optimal and that would be total system RAM. Finally it has to have m.2 NVMe SSD storage.

Holiday 2019 seems the perfect spot. 3 years between pro and a new machine looks good.

with 4 GPUs? Hell no!

GPUs are pretty difficult to syncronise, especially if they have to work on graphics (Cuda/OpenCL is much easier) since not every part of the screen needs the same amount of ressources and calculating power. It would microstutter all the time even in 60fps

PS4 Pro doesn't use 2 GPUs, just one with twice the amount of Compute Units of the base model. This was possible due to the introduction of the 14nm process (smaller chip, less power consuption and thus less heat production), but the next process update is far in the future. Intel is struggling for quite some time now with it's 10nm process (Kaby Lake and the upcoming Coffe lake are stopgaps due to the 10nm  cannonlake kept getting delayed and ultimately only ending up in mobile devices, not desktops or servers), and Globalfoundries (who are producing most of AMDs chips) stated that they will jump that process and go directly to 7nm, which is to come 2H 2021 in the earliest

As for your dream PS5, that won't come out before 2025 for sure. There ain't any Graphics card yet coming even close to 20TF, let alone surpassing it. 64GB is a giant amount of RAM. In DDR4 Memory this would cost right now already around 500$ minimum. Even high-end Gaming PCs don't go above 32GB yet, as more is useless right now unless one is rendering a lot (and even then it's barely noticeable). Did I mention that prices for RAM are going up instead of down since for about a year now because smartphones are using up almost all the production capacities for RAM?

A console OS shouldn't need that much RAM, even Windows 10 can go on 2GB (4GB is strongly recommended) and that one has vastly more functions than a console OS. What features would be in that OS to consume such a high amount of RAM?

Fast M.2 SSDs are also very expensive as they need high-end Chips which don't come cheap. 1 such as you prposed with a capacity of just 500GB costs around 300$ minimum right now. The prices are still dropping, but not nearly as fast as they did in the past anymore however, so having a 2TB or higher capacity would still get quite expensive , much more than a hard drive with x times it's capacity would do

I was just explaining it the same way Mark Cerny did. I know that PS4 has 18CU's while the Pro has 36CU's. PS4 Premium should have 72CU's. As far as 7nm goes, all I keep seeing is that we should have 7nm FinFET GPU's by next year or early 2019, making a 7nm PS4 Premium possible for the end of the year. Vega 20 is supposed to be 7nm with 32GB of HBM2.  

As for increased RAM and increased performance, that all comes down to how many people acutally have it. Right now most people have 4GB of DDR3 in there PC. Gamers have 8GB DDR3 and a 2 or 4GB GPU or a 8GB Console. Then you have the hardcore gamers with 16 - 32GB of DDR4 and an 8GB GPU or Two. Right now most programms are made with the 4GB base PCs and tablets in mind, and games are built for PS4/XBO and scaled up for PC. Once new console arrive and set a new baseline, the whole software industry will shift.

The next consoles will need massive OS RAM, becuase they will be full fledged PCs. Video and Photo editing for streamers and Youtubers will be possible in game. Running a game while having Video in a side window will be standard. Consoles will be for the majority the most powerful PC in their home. 

2025 is pretty much when I expect PS5. PS5 should arrive with 3nm fabrication, which I think will happen by late 2023 at the earliest. By then all the stuff you are talking about will have dropped massively. Samsung says they expect SSD tech to drop below HDD tech $/GB by 2020, so that will be no issue. Top end PC GPU's will be pushing 40TFLOPS by then so, even at 20 - 30TFLOPS people will claim consoles are under powered. 

Not all teraflops are the same. The GPU PS5 will use will be more power efficient than the ones the PS4 and PS4 Pro are using. Ryzen is a massive upgrade over Jaguar and there's also the possibility of Sony opting for HBM2 for the RAM over GDDR5.

I agree, 6 year update rate and 10 year support is the best strategy.