The thing is that Steem doesn't really have any control over the price elsewhere. As I understand it, the one dollar peg is a guarantee that it won't drop below one dollar.
If SBD is listed elsewhere and people push the price up, steem can do nothing about it.
They could peg it there on the internal market but that would result in more SBD leaving the system.
Eventually, the price will probably stabilize and return to the peg. But this won't happen until the new money flooding in figures out that Vests are where the value is.
Or maybe it won't. That is the nature of the free market. You have to let it find its own level and then try to figure out your play. Too much interference will only muck up the works.