Yeah, I'm not quite sure regarding SBD, but I can't imagine it will go much lower than Steem itself, since you generate more SBD with more Steem Power, which locks them to some sort of relationship (I think it's early to say exactly what relationship that is, but it is there). I can imagine a pairing of the two, where 1 Steem and 1 Steem Dollar are the same price, but it definitely could be something different. The fact that it trades on Bittrex could also make it so that SBD goes HUGE at any given time if a whale decides to go on a buying spree. :)