I think that BTC is still a relatively young currency. It takes time for people to collectively build up enough trust in a currency. It probably takes about 10 or more years for this to happen. I think that if our current global financial crisis continues to worsen, more and more people will turn to bitcoin. As a forex trader I can attest that BTC/USD is already a viable trading option even though it is less liquid than the other currencies. There are so many advantages of BTC over the USD that I don't see why it wouldn't continue to increase in value.
Also, even when BTC reaches its maximum volume, BTC subdivision will continue and miners will be rewarded via transaction fees in a highly competitive market.