Neither Bitcoin nor any other cryptocurrency can ever replace gold with itself. Gold, as a value and a means of payment, has existed for thousands of years and, probably, will continue to exist just as long. Cryptocurrency is a completely different financial asset and it must exist together with gold and national money of states. No one will replace anyone. Everything should work together and complement each other.
Gold is no longer a means of payment and saying that something is good because it existed for years doesn't change anything. People were riding on horse backs for over a thousand years and then came cars bicycles and motorbikes.
I also don't believe bitcoin will replace gold but it will take a part of the market from it. If you give a young person a choice between 100 dollars in gold or 100 dollars in bitcoin most of them will choose bitcoin because gold doesn't grow in value as fast and people are gamblers in nature.
To be fair there are physical 'currencies' that work on the basis of containing a small amount of gold which are in circulation today. An example is the Utah Goldback - it's a thin note which contains a gold leaf inside equivalent to 1/1000 of a troy ounce of gold. Comes in denominations of 1, 2, 5, 10, 20 and 50 I believe? i.e. the largest note is the 50 Goldback note which contains 1/20 of a troy ounce in it.
There are shops in Utah which accept that - so while it's not common, saying that gold isn't a means of payment isn't true everywhere