I agree with you that value of bitcoin will be rise in long term and i think should invest it but i don't think so that dollar always drops in value. It depends on the condition of the future
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So many things can happen that would render Bitcoin obsolete, the protocol is deflationary by definition, but there are many, MANY other factors that could have a negative impact on the price of Bitcoin...

Don't get me wrong, I'm a big fan and hope for a bright future of Bitcoin, but chances are high that mass adoption will be achieved by another service based on blockchaintech, please be aware of just how risky crypto atm is