Following that logic, investing US dollars into anything at all is a huge mistake. Why won't people just keep them, and don't waste their time trading?
(Hint: QE)
That is absolutely not the applicable logic, nor is it what I'm saying. This is a basic fact: Bitcoin is not a fully functional, usable currency at the present time. The reason is simply because you cannot buy very many things with it right now, and of the things you can buy, almost none of them can't _also_ be bought by fiat. It is not that Bitcoin itself is not a fully functional, usable currency, it is the material fact that a currency is only valuable when it can be exchanged for goods and services. Otherwise, minor currencies are only useful to convert into the major currency. This also applies to today's precious metals. Nobody is taking gold or silver as consideration for real world goods, but they still have value because you can convert them into the presently universal fiat.
If you don't believe it, then convert 100% of your fiat into
BTC and let me know how life goes for you. Right now Bitcoin is only worth anything because it can be exchanged for a non-insignificant amount of fiat, and is very likely to appreciate in the medium-to-long-term future.
You seem certain the current purchasing power of US dollar would, more or less, survive for 5 more years... I am not sure what this assumption is based upon.
I neither have nor do I profess any such implication. It sounds like you take the insinuation that Bitcoin isn't an economic messiah a little too personally. How close do you think the world is to accepting Bitcoin in place of or as an alternative/equivalence to fiat, exactly? You should be realistic. It's nowhere close. The mere fact that BTC isn't even measured in mBTC yet is a major indicator of how little large scale adoption there is. The mere fact that BTC can barely sustain $100 should also enlighten you a little to the realities of what you're dealing with.
Also, there is a real question of whether or not
BTC will be worth anything in five years. There's a question of what it will be worth in even twelve months. One single 51% attack, one hard fork, or one more huge speculative bubble that costs newcomers their shirts can/will severely damage or destroy Bitcoin's long-term prospects.
Bitcoin is never going to liberate mankind from the realities of the ruling system. If it ever does, it will be exclusively because the ruling system chooses to use it, and then it will fall under the rule of that system. Once Bitcoin poses a real threat, all manner of techniques and approaches will be used to eliminate it. Subversion that is hard to detect will be the real tactic that is used, and it's a tactic already being used. I have no idea how people develop such massive pipe dreams, but the world would not be what it is if people were smarter.