Remember BTC is the only real way to pull money out reliably from MTGox..
And this is why Bitcoin will ultimately succeed:
it is the superman of currency. If MtGox was engaged in the business of exchanging anything else it would be dead in the water months ago with its fiat transfer system so crippled.
Bitcoin is far bigger MtGox, and the problem of where whales dump coins is not a make or break issue. Many whale sells are trickled out over days and never detected.