Giant-Man Wreaks Havoc Alongside Wasp

So I have to assume this Ant-Man and Wasp movie takes place before the last Avengers one, right? I mean, it kinda of has to. And I wonder why they're hiding Michelle Pfeiffer in all these trailers, since it was already announced she's playing the original Wasp with Michael Douglas. Is it because all her scenes are going to be flashbacks with that de-aging thing they do now?