Gold's market cap is about $10 trillion.
Bitcoin is like digital gold—scarce, hard money not tied to a government. It's better than gold in that it's easily divisible (1 satoshi is 1/100,000,000 of a bitcoin), easy to transport, etc.
Bitcoin is becoming a global store of value; its market cap is about $350 billion. All fiat currencies except the dollar and the pound sterling has gone to zero at one time or another.
The more fiat is inflated in an unstable world, the more it replaces gold as a safe haven, store of value.
Last I heard bitcoin was not technically able to be used as a payment processor subsitutes.
It can be used for paying for things but it makes more sense to use fiat for daily expenses and save bitcoin. Why would I spend something that will be worth a lot more 5 years from now, while the fiat currency in my pocket loses value every week?
Bitcoin is already becoming the standard for large, irreversible transactions, where it excels [1].
[1] A link showing a $165,000,000 bitcoin transaction that cost about a $1.20—https://twitter.com/coinbeastmedia/status/133612299565221888...