SDR's been around for 50 years, and outside of the IMF, and over that time have actually diminished in relevance as most major governments dramatically increased their currency reserves.
Besides, the most significant currency weighting of SDRs is the US dollar, anyway (with something like a 42% weighting if I recall correctly, as well as a ~10% remnimbi component, which is a USD-peg.)
In total, only around US$300bn-equivalent SDRs have been issued by the IMF since the 1970s.
For context, daily trade in global forex markets amounts to more than US$650 trillion-equivalent
(Yes, that's trillions of dollars worth. And that's each day.)
In fact, on a dailybasis alone, there is almost as much Australian dollar denominated trade (~US$250bn equivalent) as the entire stock of SDRs in issue.
SDR's are really a bit player in currency markets, at the very best.
To suggest they might be able to supplant any other of the top 10 currencies is fanciful; to suggest that they might displace the US dollar is laughable.
