There will be performance improvements coming from an increase in IPC and architectural changes, probably around 20% at best.
This video seems to indicate up to 26% for the non-pro series but that really seems quite high compared to the improvements made on the consumer Ryzen lineup. We'll see, wait for the first reviews but in any case I can't think any of good reason to skip the new version, except for a major price hike.
The 192GB G-Skill kit seems to be the only one available in 4 sticks, I can't find 256GB in 4 sticks. Note that the Zeta R5 Neo is EOL on G-Skill website, it seems that the current generation is the
G5 Neo, and from a quick search I can find 192 and 256GB kit available. It's not on the QVL but I'll give it a shot.
Regarding SC performance, I was talking mostly about responsiveness rather than pure performance numbers. I was happy with the 5950X SC performance, the new one is great too in this regard, but I was not expecting any perceivable performance improvement in this departement. As far as I can tell the bottleneck seems to be much more on the software side, using Blender alongside C4D on the same computer I experience it everyday.
And yes I use this one daily as my main workstation. I've considered upgrading to a 9950X and then as soon as possible to it's Zen 6 successor, but even with more cores (24c), architectural improvements and IPC increase, that will probably still be much slower than a 7980X in MT applications. I already have (now) two 5950X render nodes for dailies, and I was really after that massive IR boost. Another scenario I had in mind would have been to upgrade to a 9950X and build another render node based on a 3990X (TR Zen2). It's a bit old but still powerful for final rendering, and CPU and MB can be found at a very good price now.