I think Moe knows generally what's going on. He already talked to Barzini about financing, so he must know that the Corleone financing is at risk. My guess is that he doesn't expect things to go immediately to talk of a buyout, and loses his temper.
One question I would have is: would the Corleones have pushed him out if he hadn't been skimming? My guess is that if Moe had been paying the Corleones their full share, Vito wouldn't have allowed the Corleones to go to war with him.
I think Michael and Vito saw legal gambling as the Family's future, and Moe Greene was their entree into casino/hotel ownership. He was getting pushed out no matter what.
As for what he was expecting, probably some sort of offer like he got from Barzini, presumably some financing in exchange for a stake in the business. But he didn't expect Michael to be so aggressive.
Like everyone else, he fell for the feigned weakness of the Corleone family and paid dearly for it.
