Buffet's verdict on Bitcoin may still be up in the air, but I guarantee that he'll never hold it as an investment, even if he decides that Gates was right and Munger was wrong. It suffers from the same problem that Buffet sees with "investing" in gold: gold doesn't do anything - at best, it's just an instrument - so the only way to profit on it is speculation. Real investment in Buffet's philosophy is buying something that is useful... for instance, a corporation, which consistently makes profit in a way the investor can understand and be confident in.
So really, the question is if/when Buffet would invest in Bitcoin-using businesses, and whether it'll happen because he added a Bitcoin-using business to his portfolio, or because one of the businesses in his portfolio started using Bitcoin on their own.
But he could invest indirectly in bitcoin them by buying up bitcoin companies... Hopefully gox!