I don't know the exact percentage, but most of BTC is owned by a few.
So logically, BTC can never become a store of wealth for the masses.
BUT if BTC cannot serve as storage of wealth for all and neither as day to day currency due to very slow and increasingly expensive transfers, what role will BTC play in the future?
I honestly think that it will become a billionaire's toy in the future and coins like XLM which offer incredibly fast and inexpensive transfers, will play the major role in the financial day to day transactions.
So I believe that the people who have just started to invest in crypto should consider these other coins and forget about bitcoin.
If the world will accept crypto as currency, it won't be BTC.
There are always bitcoins which are available in the market and exchanges where people can buy them. However the more people hold them, the demand become more and therefore we can see exponential growth in the price of bitcoin.
Privacy coin like XLM may be used more in the black market but they won't be allowed by the governments to use them openly.