but if ETF, SEC and PBOC legalcy bitcoin, bitcoin can strong and very long time curency, and bitcoin price can incraese very high
It was never about the ETF or any governing agency! Bitcoin was never a currency in the first place. It was just coin that way but in reality there will be no jurisdiction in the world that would recognize Bitcoins as a legitimate currency. This is because a currency, by definition, is a tender of payment that is backed up by gold or a country. Which bitcoin is neither.
"a system of money in general use in a particular country".
Interestingly, the dictionary views money as "in the form of coins and banknotes", suggesting that it would be in physical form. But when people mention that Bitcoin is a currency they nearly always mention that it is based online - a cryptocurrency. Therefore in its own sense it was definitely a currency.
But rather than worrying pedantically about whether it was exactly a currency, we can just say that it was definitely intended as a means of transferring goods - one that was convenient and decentralised and the idea is very good. Unfortunately, OP is right that in many cases, it is viewed as a stock. But I do believe that Bitcoin can get past this hurdle. I don't think that having a deflationary currency inherently results in hoarding because people still need to buy things in their lives. The only issue is scalability and Bitcoin's community is principled enough to genuinely make progress because as soon as we are past this we reach a new stage in which Bitcoin can (potentially) be used in everyday life.
It can even be both an asset and a currency which, frankly, is just win-win for people who take part and encourages people to use Bitcoin. There are so many uses because they could even buy other assets with what they already view to be an asset.