Here some new thoughts of mine after re reading 212 and thinking through.....
Looks like all of these sorcerers of the past have a sort of binding vow with Kenjaku, which involves fighting Sukuna at some point.
This means that we are about 100% guaranteed to see a magnificent Sukuna vs All at some point, but not for the reason we might think!
I wonder if Sukuna has a similar binding vow with Kenjaku, where Kenjaku needed great amounts of CE and Sukuna wanted another 1 vs All so they made a binding vow with one another, where Sukuna would have provided the CE and Kenjaku would have gathered all the strongest sorcerers through time for Sukuna to fight them.
Now i also wonder if Kenjaku ( knowing Sukuna lol ) wanted to find a way to respect his binding vow with the other sorcerers but not with Sukuna, so he tried to engineer the perfect vessel that could not only host him but keep him caged ( maybe that's why Sukuna was surprised he couldn't take control of Yuji right away ) so if the other sorcerers were to fight Yuji they would have also fought against Sukuna, without the need of Sukuna to be in control.
Maybe Sukuna knew Kenjaku would have tried to" trick him " so he made some other arrangemens with Uraume, and when he realized whatever he realized about Megumi's technique instead of making a binding vow to permanently take over Yuji ( which he could have easily accomplish imho ) he decided to wait for Megumi to mature enough and in the end take a gamble to take over his body maybe even freeing himself if he had a binding vow with Kenjaku, cuz he now found himself a new vessel so he's pretty much free to do whatever he wants...