I was sending internationally with DHL - when the impact on flight travel started to happen, it was not long before services to certain countries were cancelled, and multiple surcharges were introduced on packages to countries where I could still send things.
One was because the AUD fell so low (I watched it freefall all the way to 56c before it started to bounce back a little, though I heard it went even lower briefly) that discrepancy had to be covered, and the other was because significantly reduced flight availability + increased demand for cargo space meant higher costs to get things on planes.
Australia Post has also suspended all economy (untracked) services - I suspect this is primarily to reduce the demand for cargo space as well as to ensure the flights taking cargo are cost-effective.
All of which I mention because I doubt we are unique here - cheap services are mostly out or at least being discouraged, and for many the higher-priced tracked services are subject to continually changing costs.
Things will only start going back to normal when people all over the world can travel freely again. I think things will settle down and level out a bit sooner than that (since I doubt the above would occur without a fully functional, safe vaccine, and if that's even possible, it'll be around 18 months before that will even start to come into play), but these factors will be affecting postage services and their costs for a good while yet, IMHO.
