There are scenarios in which the Bitcoin "sector" grows without the value of Bitcoins themselves appreciating significantly (or at least, to the same extent). For example it could become a common medium of exchange but an uncommon medium to hold, if a large portion of the growth is in Bitcoin exchange platforms that convert payments immediately to national currencies, like BitPay. In such a situation there could be a large volume of business going through companies like BitPay, but with only transient demand for the coins themselves.