The pied piper always gets paid. ( German Legend a musician who rids Hamelin of its rats by leading them with his piping to the river, where they drown: in revenge for not being paid, he pipes the village children to a mountain, where they disappear)
We're actually conflating two related but different concepts at this point. The extent to which trade is denominated in dollars is a different thing than the amount of foreign reserves that are denominated in dollars. I think when most people refer to "reserve currency" they're talking about the latter, while you're talking about the former.
They are of course linked. The reason Central Banks have so much in dollar denominated reserves is because so much trade has been carried out in collars. They can use these reserves to both facilitate foreign exchange and to manipulate the currency market to maintain (or try to maintain) a favorable exchange rate for their own currency relative to the Dollar.
What a joke. It is if central bankers know a good rate is for their country beyond the next 24 hours. They know less than you.
Knowing the real cost of money went out the window years and years ago. Yet I doubt the "famed" Economist Keynes could even recognize that.
I read an interesting book on this a while ago called "The death of money" The author spents a lot of time talking about BRICS as a potential alternative, but didn't really provide adequate consideration to how much many of those countries distrust each other. I feel this point is also skipped over too much by those looking towards China. People use the US system because they have at least some trust that their money is protected by at least vaguely credible court system. I think trust in the US will continue to erode but it's still the prettiest girl at the dance by far. Imagine as a foreigner being caught up in a Chinese version of MF global trying to get your money back.
The $US like most currencies are not anchored to anything. Therefore it is fading as a reserve currency and no other currencies are becoming reserve currencies. Hence the rise of crypto currencies is the proof that fiat currencies are fading into history's dust bin.