The impact from the RTX 4090s in BAK was minimal since DPC started doing 60fps animations (and some 90/120 ones too for some god forsaken reason) around the same time he upgraded his PCs.
The RTX 5090 will be quite powerful as I
said before, the bigger VRAM would be specially useful for DPC when he needs to render complex scenes like the costume competion scene with all the party present.
He also mentioned running out of system RAM as well while rendering, so a PC upgrade wouldn't go amiss.
Of course we can't say for certain how much that would improve speeds, like you said DPC can always find something to waste most of the power from it.
I doubt he would do 4K, but he could easily tweak some DAZ settings to improve the render quality in a very minor way and waste all the perfomance.
However, I doubt he would upgrade his GPUs this soon though, it would be a substatial purchase (even if he could afford it with just a month of patreon money).
Lets hope the eventual backlash from EP 11 taking more than a year be enough for him to feel forced to do it, but I doubt it would make the time between updates fall below a year.
EDIT: Some extra info.
DPC annouced he was upgrading to the 4090s in 07/04/23, roughly 6 months after they were released during EP 10 development.
Yeah, DPC is immune unless he does something completly retarted, which he won't, since as much as we like to insult him here, he is not dumb.
Also Geralt, since you are a DAZ user, would you say that DPC could increase the light rays amount in his renders to "lose" the extra performance from an eventual upgrade to a RTX 5090?
You know, this makes sense, I doubt DPC wants to waste time banning people in discord.
I bet some, not all of course, shit we say about DPC is some overzealous mod fault.