How would the world have evolved had Judaism died off in the first 50-100 years after the destruction of the Second Temple? We can imagine the Romans deciding not to allow the sages to keep their academy ("do you REALLY expect us to think that you're just going to "study" there?). Combine this with the explusion of the entire community and forced assimilation. Without the sages and rabbis trying to modify the tradition to reflect a missing Temple (and no more "prophets" to talk to the people), we can imagine that Judaism disappears.
Note that Christianity is going to survive, in all likelihood. By the time of the destruction of the Temple in AD 70, Paul has already done his missionary work. The Christians may believe that this is as sign from God that they are the Chosen People and that God, in his mercy, had prepared Christianity as Judaism's replacement in a world with no Temple.
So we have Christianity without Judaism. What happens next? I can imagine the Middle Ages having trouble (who gets to be moneylenders and so forth?)
ACG