Is Ripple an anti central exchange that makes Bitpay and Mt.gox almost obsolete?
Ripple supports a distributed currency exchange; anyone can offer to exchange from one currency to another. These offers are taken when a counter offer the same or better is made.

Like any exchange between two parties, the price would be based on supply and demand, world events, what the market will bear, etc.

The advantage is there’s no single point of failure that would cripple the market. We’ve seen what happens to bitcoin when Mt. Gox goes down or is under a denial of service attack. That’s obviously not a problem with decentralized exchanges.

And with the new Bitcoin Bridge feature of Ripple, you can pay anyone in Bitcoin from a Ripple wallet. The currency exchange is done by an organization (a.k.a a gateway I believe) running the freely available Bitcoin Bridge protocol, like Bitstamp. You can see as of this moment, the Bitstamp rate is $98 per Bitcoin. You can see the exchange rates of the exchanges at Bitcoin Average.