The point of these demonstrations isn't to showcase what games will look and play like all generation long... But to showcase the individual rendering techniques and technologies that will define the games thanks to new hardware feature sets that enable them.

Unreal Engine 4.0 was showcasing the new Tessellation capabilities, Asynchronous Compute which gave us some impressive material shader effects, Cloth Physics, Post-Process effects and so much more.

Again... These demo's are NOT representations of what games will look and play like all generation long, that isn't their purpose, it's showcasing new technologies and effects, that is their purpose.
Unreal Engine 5's demonstration is it's all about it's new geometry technology, Nanite and the Ray-Traced lighting effects, Lumin, not what it means for gameplay or future graphics. - Developers will leverage those technologies in different ways, even build upon them to make them even more impressive... And that is truly something to get excited about.

Not saying it wasn't surpassed, but it does date to well before this gen started instead of the eve of the 9th gen, so I don't think it's a 1:1 comparison.

That's my point entirely. That games will surpass what's shown in these tech demos. I was responding to

"If actual shipping games can meet or exceed the quality of the UE5 demo, then the jump from PS4 to PS5 will impress me more than the jump from PS3 to PS4."

and saying that UE5 shipped games will definitely look better than what's shown in the tech demo. And using a past example to back up my claim. 

That's why I mentioned games made using UE4. Games using UE5 will 100% look better than the tech demo we all saw.

If actual shipping games can meet or exceed the quality of the UE5 demo, then the jump from PS4 to PS5 will impress me more than the jump from PS3 to PS4.

I'm happy with how my Switch games look for the moment; when the times comes I would hope it's successor can exceed the PS4 graphically and incorporate some of the advances of PS5/XSX.

Sounds very much like the typical Chinese offering where devices get tricked into showing eight times the space of what is available in reality. So your example would actually be an 128 GB card advertised as 1 TB and $45 is a rather high price for that; but that's the point of the false advertising, to sell the same amount of storage for a higher price while suggesting that consumers are getting a good deal. What makes matters worse is that those cheap SD cards have also common problems with reliability, so they stop working fast. They are an all around bad option.

The current Switch can straight up run full blown high end PS4/XB1 games. 

It's just a little cramped to do it and there are cartridge storage issues to account for also, but it can do it. 

Switch 2 will be able to do the same for PS5 more easily with DLSS factored in and larger cartridge sizes also I think. 64GB cartridges will likely become reasonably cheap and 128GB may even be an option fairly quickly. 

If Switch 2 can exceed PS4/Xbone to the extent that Switch 1 exceeds PS3/360, and be roughly the same distance from PS5/XSX as Switch 1 is from PS4/Xbone, I'll be happy.

I think with the technology we -currently- have available, we might see around Xbox One levels of performance with the Switch 2, if Nintendo adopts nVidia's latest SoC which is a big ask.

We already have LPDDR5 which can increase bandwidth by 50% over LPDDR4X (Switch uses older/slower LPDDR4), so 50GB/s of bandwidth should be possible for a Switch 2... Which is roughly what you want to start touching full 1080P.
LPDDR5X might be a thing by then too... Who knows.

So if that's whats currently available, any idea about what could be available for a release in 2023?

Unless Nintendo does a 180 and decides to make Switch 2 with the latest and greatest, whatever is avaiable this year or 2021 at best is probably what's going inside of it - even Tegra X1 would be too costly for them if nVidia haven't flopped so hard at selling it (I don't think there's actually any devices outside their own that use it), thus eventually making it affordable for Nintendo.