"Until the become conscious they will never rebel, and until after they they have rebelled they cannot become conscious."

This statement is referring to the hopeless circle of everlasting oppression that the proles were in. For they cannot rebel until they realize that they are being wronged in the first place, but if they cannot realize they are wrong until after their rebellion. The problem is that the Oppressers won't allow them to realize that they are ever being oppressed in the first place.