The fundamental allure of bitcoins seems awfully ideological, so I think the idea of a decentralized, P2P exchange is the only thing that can save BTC at this point, so I've high hopes for the current projects in that area. Anything else is prone to manipulation, which really defeats the purpose of BTC.
I actually didn't mean a legitimate service to replace all current exchanges. I simply meant one to come in and take over the majority of trades. Once that happens other currency exchanges with histories will step in and it will be more decentralized. I think a company like Forex is less open to manipulation than Mt. Gox but, that is just my opinion.