How popular would it likely be? How popular would you want it to be? How inflammatory or controversial would relevant subject matter be?
For most new communities, traffic will be low and manageable, and you can play it by ear. Start it and see what happens. Post it in the New Communities sub if you want to get some eyes on it, or just let it grow organically.
This is all terribly engaging!
Were you born a greedy little pigboy? Or did you have to learn how to be?