Dunno. With all the symbolism in Revelation, it could mean a lot of different things. To me, it sounds like the kind of things the Qumran community said about one they called "the Liar". If there is any connection here, "Jews who were not Jews" could refer to Jews who rejected the Torah.
Steven, look at some of the language in these passages (Revelation 2 and 3): "poverty", "rich", "throw...into prison" (similar to "cast down"), "Balaam", "Balak", "food sacrificed to idols", "immorality", "I know your works", "those...who say they are Jews and are not, but lie", "he who conquers I will make him a pillar".
This is not hellenistic Christianity!
Yes, very telling language in those verses. I happen to believe John avoided thehellenization of that period. When he referred to "jews who were not jews" he probably meant those who say they are God's people but really arent.