I don't understand why the value of Bitcoin needs to be derived from goods for that to happen. With people thinking of the value of bitcoins in terms of what their local currency can buy, we should still be able to say that 1 USD can be bought or sold for 0.0833 BTC. We should still be able to talk in terms of using bitcoin to buy or sell other currencies.
That's because we naturally derive value from the things we are consuming most of the time.
I played DiabloIII for a while for example, there lets say a useable 1-Hand weapon is worth about 1,000,000 gold a useable chest plate about 2,500,000 and so on. The same things are also sold for paypal and credit cards on another auction house, but those prices are derived from their respective gold value not verse visa. That is because most people don't use the Real Money Auction House and prefer to trade using the Gold they collected while playing the game.
In order for that to happen (naturally) Bitcoin needs some niche market where it is used as a primary currency, just like the ingame gold currencies do.
It seems you are proving yourself wrong with this very example.
In your example, the "new" currency is DiabloIII-gold. This currency is valued in terms of goods (weapons, chest plates, etc). And yet still, I assume, when exchanging DiabloIII-gold with USD, you don't refer to buying dollars with DiabloIII gold, or selling dollars to get DiabloIII gold. So even though the currency is valued in terms of goods, you still frame your discussions about currency exchange in terms of buying and selling DiabloIII-gold for dollars rather than buying and selling dollars for DiabloIII-gold.
Clearly valuing a currency in terms of goods has no bearing on how people think about the currency exchange with other currencies.