At that point, the people with the massive computing power are going to have incentive to throw at least some of these Bitcoins into the market just to generate more trade volume.
Bitcoin's exchange rate against the USD has no bearing on its utility as a token of exchange.
With fast enough exchanges and sufficient enough liquidity ("enough" being the key word) the total amount of Bitcoins in circulation doesn't even have a large impact on trade volume. Bitcoins don't get consumed in the process of trading.
Therefore I don't see how those with massive computing power (for generating income through transaction processing) benefit by selling previously-hoarded coins. If anything they benefit by not selling their coins, maintain artificial scarcity and thus high exchange prices since they get paid in coin.