(BitCoin is doing well right now because of the Cyprus crisis.)
I have no clue about its directional future, but I can see it being, for the next 10 years, a way of betting against the world-- a distinction that gold used to have.
Either a major calamity like government intervention will end BitCoin, or it will be supplanted by different technology, or BitCoins will appreciate for decades. They will either be worth zero, or a lot in my estimation.
Disclosure: I own 20 bitcoins.
If you buy BitCoin, you're betting on the prestige of its being the first. Do people even know what the first fiat currency is? Or care?
People who sell at the top of BitCoin are going to make a lot of money, but for the long-term value, I'm betting on zero.
It is a fair point that there could be other competing, but not dominant currencies, which could lead to a non-zero, but low price for bitcoins. So perhaps, 0, a lot, or anywhere in between for the value of a bitcoin.
As long as the number of things you can buy with bitcoins rises over time, the value of bitcoin will rise. I don't think it is unreasonable that the momentum, including technology and community (not just brand around BitCoin) will make it a favored son in digital currencies. So it's not just buying it based on the prestige of being first, it's buying based on the value of being first. I actually bought my coins when YC invested in CoinBase, because I thought that was a strong signal.
It will be an interesting future where people buy currencies based on their mathematically-dictated value profiles, as opposed to whichever currency is sold by the local government, and _seems_ to be the most stable.