In the long run, no. Bitcoin is still a really good idea, and if satoshi dumped a couple million BTC, the market would absorb them. Sure, the price would drop, but given time, it would also recover because there is value in the very idea of Bitcoin.
The same would be true once Ripple was open-sourced.
Let's wait till OpenCoin opens Ripple and see if it truly becomes decentralized, then there might be ways in which it could complement Bitcoin. Right now, it doesn't.
Is Mt Gox helpful to Bitcoin? Is it open source? Is it distributed?