This whole house of card is very modern, there was no such thing as "Reserve currency" not even the British pound, it was the most traded currency. but holding a currency's (debt) as a foreign reserve instead of gold is very recent phenomena, even central banks reserves or their function is also rather modern phenomena.
while Yuan usage in trade will reduce the US influence, the amount of assets held in dollar nominated investments is so so much bigger, and this will very slowly change if it will at all.
The pound did act that way to some extent, but only within the Sterling Area and only between 1931 to 1972.
Prior to that, people might have talked about the pound as if it were a reserve currency in the same way the USD is today but, as you say, actual foreign reserves were based on gold.
Very telling that even top economists are unable to imagine a world without a reserve currency when that is the state of nature (even in antiquity there were multiple currencies, not just gold)