The price of a HDD is 35 $ incompressible. The only difference is storage size growing during the time. One day it can be 3 or 4 TB for the same price.
All mechanical and eltecro mechanical part + optical drive and HDDD of PS4 were 100 dollars of PS4 cost at launch and because of mechanical part there is an incompressible price as much as the SOC... I am sure using a custom SSD 256 GB like in patent + a 2TB HDD against a 1TB SSD is probably a little bit more expensive at launch and the cost difference grows in time...
I was talking about Microsoft only, not Sony, I do think Sony is using a one big 1TB SSD. Microsoft can't use that patent so anything regarding the patent is irrelevant.
According to the table you've brought in this post, the One had in 2013 a 500GB HDD with 8MB cache for 37$. In 2016 the One S had a 1TB HDD with 32MB cache
for 32$ and the 2TB HDD with 8MB was 55$. Today, a 256GB NVMe SSD cost ~1/4 the price of a 1TB NVMe SSD. The total BOM at launch should be more or less the same for a 256GB SSD cache drive + 2TB HDD VS 1TB SSD.
Cost after launch is irrelevant. Consoles go through revisions all the time, they switch HDD models all the time. If your system knows who to work with a cache SSD + HDD, it also knows how to work with a pure SSD storage solution. If after two years having a single 2TB SSD is cheaper than using 256GB SSD + 2TB HDD, they will just use a pure SSD solution at that time-frame. There is no need for future proofing your machine storage wise as long as you upgrade your storage and never downgrade. I'm pretty sure that a pure SSD solution is an upgrade, so no problem there.
Regarding repair and warranty costs, the HDD doesn't have to be included in the warranty. A lot of appliances cover only certain parts of the warranty. If you have an easily replaceable HDD, anyone can go to the store and buy a new one for 40$ or just use an external HDD so no real problem there. If you want to worry about anything, worry about the SSD soldered to the motherboard. If anything happens to it, they have to replace the whole thing.
Okay, so this would mean actual HW design alteration at CU level to do something like that. From what I have read, Tensor Cores are something akin to Blackbox and so there is no actual breakdown of how nVidia designed it beyond documentations provided by them that show how to make it work efficiently (afaik).
On the AMD side of things, I think they had a patent about some "Hybrid" version of the RT. Now whether that would necessitate in apportionment of existing CUs into something akin to tensor cores or having separate set of CUs in their own cluster dedicated to RT or something else is unknown to me.
Whatever the case may be, the die size will most likely not be 251mm2.
If I remember correctly, and
chris 1515 probably read the patent much more thoroughly than me, in the AMD RT patent they want to take the TMUs and change them into something called Texture Processor which will also have a BVH intersection check unit. There are 4 TMUs inside each CU so if the PS5 will have 40CUs, it will have 160 Texture Processors (which also does what Turing is doing in order to accelerat RT) with each additional CU adding 4 more Texture Processors.
This is an RDNA CU, the lower part is grayed out because that's the second CU that share its' resources. The yellow part on the right are the four TMUs which should be replaced with something larger called TP (Texture Processor) that does both the TMU's job and RT BVH intersection checks:
Again, if I got something wrong please correct me because I read this patent weeks ago without diving too deep.