I don't know the yastic used by these banks that are selling gold so they can invest in Bitcoin because Gold is one thing that countries stored their wealth on because of it's value because gold is one commodity that never depreciate making it one of the most valued commodities on earth many people will not sell their gold in the place of Bitcoin.
Bitcoin is one thing that is revolutionizing the entire financial sector as it's now a means of investments so I will not advice anyone to sell his or her gold so that they can buy Bitcoin as Bitcoin of them are stores of value