Yasuo with the New IE + Conqueror

TBH I'd wait because there are arguments he's gonna be insanely strong with new IE and Conquerer and there are arguments where he'd actually be weaker after IE changes.

One thing for sure is, IE and Conquerer do not go together. They both take damage from physical damage dealt so you'd actually do less with old IE and Conquerer vs new IE and conquerer

Except for the fact that Yasuo does less damage from critical strikes, so he'll get less true damage from IE than others.

ADCs really aren't hurt by the item changes, it's a lateral move overall, however champions such as Yasuo will be further nerfed and while I realize that about 75% of the Boards (and playerbase alike) will be happy about that notion, it's not good news for the viability of a champion that already struggles in higher MMR.

Yasuo won't take conqueror with the new IE unless in very rare exceptions. It doesn't scale additive and he will need the additional flat damage to make up for the IE crit nerf.