During Olympics a commentator on Eurosport said that Yuzu is not the only skater aiming for the 4A debut. Chafik Besseghier from France has practised it successfully with harness already and a Russian skater (his name was not mentioned in particular) has landed it without assistance - allegedly - but fell on another attempt and broke his leg.
I don't know how eager Yuzu is for becoming the first skater to land the 4A. If I remember correctly, he said something like "I wouldn't be disappointed, if I wasn't the first, but I want to master it in my competitive career."
But let's be honest, guys. I bet my monthly salary that he wants that crown for himself. The 4A is his little baby and he doesn't want to see anyone else land it before him

So he won't wait too long. I'm quite sure he plans to attempt it on the big stage - that will be GPF 18 in Vancouver (former Olympic venue) or Worlds 19 in front of his home crowd in Saitama.
#Sidenote: I don't think that he'll quit his competitive career after the 4A debut. Yuzu talked about the 'perfect skate' as his long-term goal. No way he can achieve that within a single season (beat me, if he can :hopelessness