TBF even if the ref didn't rule that a low blow, I think USYK survives and wins. He was hurt, but he was also trying hard to sell it to the ref. There's a chance Dubois would've got him out of there but I doubt it, Usyk is wiley and Dubois ain't a killer.
What's clear to me though, after watching the last two Usyk fights is that Usyk whilst still elite, is definitively past his prime and quite beatable. The most notable signs of his decline are in foot speed and upper body movement. Usyk has some of the best feet we've ever seen in a big man, but there's less lateral movement, and he's much more hitable. He's been able to evade jabs of rangier fighters with his constant circling and head movement, and is generally good at catching left hooks to the body on his elbow. He's never had a good defence for the right to the torso though, and has had the fortune of being in against guys too timid (AJ) or too slow (Chisora) to really exploit that weakness (Though I dont think he beat Breidis). That combined with his crafty (and annoying) trait of complaining to the referee whenever he takes legit body shots.
While Fury isn't much of a body puncher and looked bummy against Ngannou, I don't think Usyk has the feet to constantly move and dart in and out of range anymore, and will get picked off from outside.