I was a bit baffled by Sony's presentation but I have to admit that the SSD tech definitely sounds like a game changer in the way game worlds can be realized and how we move around in them. However, if developers would fully embrace the tech and build their whole games around it, how will that work on Series X and how about pc? 

Xbox SSD is slower but the games should behave very similarly.
For PC with HDD I don't know how that will work, perhaps compensating on RAM.

I think third party devs will use the lowest common denominator for the consoles. So most likely, most third party games will be limiting to the performance of the XSX SSD assuming the rumoured XSS isn't slower. Ps5 will still have some advantages even then when it comes to loading and etc but I think most third party games won't take full advantage of that SSD in terms of developing around it.

As for PC. I think soon enough, PC gamers that are still using Sata based hard drive or SSD will need to upgrade to Nvme otherwise they are gonna see hitching and stuttering. Similar to if you look at the Fallen Order performance between hard drives on consoles and SSDs on PC. I think (but I could be wrong) there are a good amount of Nvme drives out right now that can probably handle XsX's SSD speeds like the 970 Evo.

https://www.samsung.com/semiconductor/minisite/ssd/product/consumer/970evo/

Won’t make much of any difference just like the cloud didn’t for Xbone. They’re both secret sauce type features that people make a bigger deal about than will play out in reality.

I really hope the SSD isn’t clung to as tightly as the CELL was. PS5 is focused more on utility where as Series X is raw power. Both should end up being pretty similar in performance and game design. The multiplats will be the true comparisons.

For PC, make the switch to NVMe 4.0

I did and I'm never going back to those sata SSDs.

For PCs wth slower hard drives, you need to compensate the slow speed of the storage with a lot of more memory.

We do not know.

What people don't seem to understand is what was actually solved by Sony. Whether Sony spent too much money on this (and sound hardware) and sort of forgot the rest (I'm not happy at all about the memory bandwith, for example), only time will tell. Here it gets very technical, but the short version of it is: Sony can stream into gpu memory space with gpu cache coherency, and do this at very high speeds. No ssd/pc combination in the world can do this. Yes, there are very fast ssds available for pcs, but they all stream into cpu memory! The XSX also streams into gpu memory space (not quite at the high speeds as the PS5), but MS has not explained how they solve the problems associated with that. The cache scrubber (and possibly whatever is in the Kraken hardware) is proprietary to Sony, so MS doesn't have that.

I remember a demo of AssCreed where the guy runs through a crowd. Often people and stuff appeared out of nowhere (what is called popup). The faster the guy ran, the more popups, very annoying to watch.

Now on the PS5, these popups are entirely gone if you program your stuff "the correct way". Even when you turn around your warrior and s/he looks elsewhere and a whole new lot of assets have to be loaded - no popups. That situation can easily get completely out of hand when you use ray tracing in building your scenery, as your gpu caches might no longer contain large parts of the correct scenery.

The games will show us the truth. I imagine that a game tailormade for the PS5 will run atrociously on a pc, if it is a simple port to the pc (whatever that means). What the XSX does with such a game is anyone's guess at this time of (not) knowing the intrinsics of the gpu hardware, but I can imagine it will require some additional work to "get it right", a simple compiler flag setting won't do the job.

I think PC's will be fine. I'm planning on upgrading to NVMe's at some point near the end of this yr or the start of 2021. I've already got 5 SSD's running, so I'm doing fine with loading times and texture streaming thus far (save for older games like RAGE, which were just bad in general with their mega-textures).

I also think that ports to PC will not run "atrocious" either, especially considering the list of good ports we've had this gen (DOOM being the Crème de la Crème).

What I'm hoping for is volumetric approach (about bloody time), whether it's sparse voxel octrees or something else, where massive amount of fine detailed persistent world data is kept on SSD and streamed into RAM. There's been move in that direction from some indie/small devs, I'm waitng to see what big budget devs can do.