Bitcoin is still being used as currency because you can pay in millions of merchants with bitcoin and its still dominant whole cryptocurrency space.
Therefore bitcoin is both investment and currency, in next few years we will have lightening network which will make bitcoin ultimate payment gateway.
Bitcoin might keep on holding speculative value in future too but volatility might get lower down with increasing marketcap.
Yes! Once the market gets larger (much larger) volatility should decrease significantly. The plus the lightning network will set Bitcoin up for use as a currency. Currently right now with its volatility, people view it as a speculative investment. I do think Max Keiser is correct in stating the price will stabilize at around $100,000 USD.
Bitcoin failed as a currency? I don't think so, First we should understand the difference of FIAT money supported by its Government Financial institution and Bitcoin as Digital currency transaction. If you look the trading market Bitcoin surpassed other crypto currency coins posted after ICO. Bitcoin once adopted by this Government and Regulation as main Digital currency then we can say that it had gone thru the process of acceptance by global economic Market Trading.Remember Bitcoin as presented to the crypto market, it is Decentralized currency, that's one reason why it faces the issue on regulation. I am optimistic that Bitcoin will be adopted by global community as alternative currency.