True, but something has to give at some point... meaning at some point the intended performance requirements of the hardware will dictate their choice in hardware. Like pushing for GDDR5 ram as opposed to using the cheaper DDR3 ram back in 2013. Or the XB1X using GDDR5 as opposed to using DDR4 ram which would have been cheaper for them too.

When pulling as much data as 4k games (with those larger textures and all) require to fill say at least 16GB of system ram (and even worse if its more than that) loading times will be a lot worse than they are right now. So it may be necessary to look at faster storage solutions.

But let me be realistic here (and more specific), we both know that you don't need nvme speeds for games in general. Be it PC/consoles. SATA 3 (600MB/s) speeds are more than enough and this is evident in looking at games running on the PC on an Nvme drive vs the same game running off a SATA 3 SSD.  So all they really need in those next gen consoles is a SATA 3 SSD. Right now you can buy a 500GB SSD for like $100. Thats definately not what sony/MS would be spending for them. My guess is that around 2020 sony/ms should be able to get a 1TB SSD for under $50.

The real important thing is that their build an I/O bus that actually really takes adavntage of those kinda speeds.

Even better, everything I just mentioned carries over to the M.2 format. Lets not forget that there are also M.2 SATA SSDs. And yes, right now you can buy a 500GB M.2 SATA 3 SSD for as little as $100 on amazon and even less if you are going with cheaper brands than Western digital or samsung. So sony/ms could very well totally ditch the 2.5" form factor completely and instead go with a PCIE M.2 interface (that supports nvme drives but ship their consoles with a SATA M.2 drive instead allowing consumers the option to upgrade their drives if they ever see the need to.

I really believe that by 2020, sony/ms would be able to order M.2 SATA 3 based 1TB SSDs for under $50.

Hehe.... nope I didnt't. And you are actually saying exactly what I was implying too. Yes, you only would need 4 chips for 8GB of DDR4, and that is my point exactly. This is why I keep saying LPDDR4 (as used in phones), cause for that you will only need one chip or should I say one "package" that is the size of one chip of GDDR6 ram. 

Now if you are looking at a system where you need to have 16GB of DDR4 coupled with say 16GB of GGDR6 then you will need to have a PCB thats big (and complex) enough to accommodate 16 total chips flanking the APU. And this whole thing will be ridiculously expensive too.

But using LPDDR4 (like the ones used in phones), you would need only one chip to get 8GB of ram, 2 for 16GB, leaving a lot of room for the GDDR6 chips. And LPDDR4 ram is significantly cheaper too.

Unless I am mistaken, no... not with LPDDR4. To my understanding its peaking out at 32GB/s. That however may be due to a smaller bus used in mobile phones and could be different in a console if they use a larger bus but I don't know about that so I can't say anything since I couldn't find anywhere that it was used like that. But theoretically I don't see why its not possible.

Which coupled with what your confirmation that any Ram technology can benefit form bandwith increases when paired with other similar ram in a unified bus means that its even better for my theory. Sony/MS could go with two 8GB LPDDR4 chips to get 16GB of OS and CPU Ram with a bandwith of at least 60GB/s or higher if the whole wider bus for LPDDR4 is possible. Meaning they could lock out 8GB of this ram just for the OS and make 8GB available for games coupled with what will now become the at least 8-16GB of dedicated GDDR6 vram.

Im ready for 2020

Once large SSD's hit that price point, then all bets are off.
We are still awhile away from that point though.

... And NAND manufacturers switching over to GDDR6/DDR5 is going to slow that down.

PCB size isn't the issue.
It's the number of traces and thus layers that becomes problematic... And that increases exponentially with the amount of chips you add.
Some DRAM chips need less traces than others as well... So sometimes when you do have twice the number of chips, you don't need as many traces as thus layers.

But it all comes down to price in the end, if they can get high-capacity LPDDR4 cheaper than regular DDR4, then that is probably what they will opt for.

You certainly are mistaken. We just haven't seen LPDDR4 implemented in such a way that pushes past 32GB/s of aggregate bandwidth.
It can most certainly go higher.
The more chips you add, the wider the bus you implement... The more bandwidth you have at your disposal.

It will be interesting to see which way they take things. I doubt Microsoft will go for split pools anyway, they haven't actually done this in a console yet, where-as Sony has done it for the last few generations.

There are Pro's and Con's to it as well, when Microsoft/Sony optimize their software stacks and free up more memory, it's more beneficial to a developer if it's high-speed GDDR6 than DDR4/LPDDR4.
Split pools also means you take a small bandwidth/latency hit when communicating/shuffling data between them as well.

I have a little experience with PCs. My ex-boyfriend is a Computer Engineer and knew a thing or two about this stuff. And i totally agree with you. I just don't see those consoles with more than 20GB or so of ram.

But there's another possible solution for overpriced RAM issue: postpone launch until 2021.