Another possibility for a decrease:
A major holder of bitcoins tries to pull more than can be converted into a national currency. This basically topples what I equate to a ponzi scheme when people find out that it doesn't convert so easily back and forth at current evaluation, and reduces the value enough that others fearful of loss start to try to convert as well.
I think that this is probably the most likely scenario where people discover that bitcoin, as a currency, is a bad idea: deflationary currencies cannot succeed (the rate of creation goes down while population goes up, so it must be deflationary). Further, it shows that bitcoin as a commodity/investment doesn't work, because to be honest there is nothing backing it up. What recourse do you have when the bitcoins you bought at 10k are now worth 1k? What real gain/loss has occurred that the rest of the GDP need concern itself with?
Philosophically, I believe that bitcoin has presented an interesting technological breakthrough, but the implementation of production is off. I do believe that in the future that we'll see national currencies using blockchain technology.
In the meantime, I'm not going to worry about it, and I'm not getting involved. If some of my friends become wealthy for it, then great for them, but I'm not particularly keen on 'get rich quick' or market timing schemes.