Gold is a safe investment both for short or long term investment. The characteristic is not volatile, it will keep increasing along the time. However, the increase will not jump as high.
Bitcoin is a very promising investment, you can gain high profits only in a short time. However on the other hand, you may also lose a high amount in a short time. For, Bitcoin is high volatility, it is always fluctuating. We can control the price of BTC because the price will depend on the market.

I will not think about it because BTC will not replace gold. The two will exist and develop together without another should be replaced or replacing. They are a great investment for all.