This is the biggest deathflag in existence.
I doubt Sukuna is that type, he is too proud of his strength to ''cheat''.
Pretty much this imo...
Ppl clearly underestimate (current) Sukuna. The Fallen one and King of curses is not only insanely strong (and we havn't even seen him fighting seriously yet), but also a fighting genius.
His intelligence concerning CE/CTs use(s) is unmatched (hence his title). The whole fight against Yorozu's was a showcase of it.
He not only (no diff) defeated and tamed Mahoraga (what no 10S users never could do), but also understood its exact potential and usefulness in no time.
And that's the main point concerning the incoming fight: as no one never tamed Mahoraga, no one ever used its full potential, therefore no one know how tricky/hax it is when fully mastered.
The 6th eye wont change anything as we know a 6th eye user with limitless CT already lost against an untamed Mahoraga.
That's not all.
We know that killing a shikigami creates a stronger one. If Sukuna sacrifices on purpose all of them he could create something beyond imagination: Mahoraga with the abilities of all the others shikigamis, especially Madoka, would be literally invincible, even for Gojo.
Besides Sukuna can most likely uses the chimera garden domain perfectly, a domain in which he could summon multiple Mahoragas at the same time. Destroy one: the others will adapt.
Last but not least: I wont be surprised if Sukuna could mix his own domain with Megumi's. "Chimera malovolent shrine garden" (lol).
And we're just talking about the 10 shadows CT. We don't even know what is 20 fingers Sukuna capable of, nor his actual CTs.
Gojo will 100% fall against the fallen.