There is absolutely no way that 780 sells out in volume at $700. People who were in the market for a high priced card are already tapped out with the Titan. Anyone waiting for a $700 card , probably has already spent $1k for the Titan. There is no market for a $700 card at this point. If it appears that it is selling out, it would be because not many were produced.
However, that would not make any sense. The Titan owners have already spent their money, why in the world would Nvidia care about what the Titan owners think, as we are not the future potential customers for the 780.