Take a deep breath. An iMac redesign is monumental. It deserves a keynote. Apple could have had plans to do a March keynote which was sidelined by the virus. Or they could have always planned the keynote for WWDC. Either way, "ready to ship" is not necessarily substitute for "there are warehouses full of them." Ready to ship can (and does) mean different things to different people.
I have to agree with gusping, if there are iMacs that have been ready to go since March, I can’t believe they are the same iMacs as the redesigned iMacs. I think either one or more of the rumors we’re working off are incorrect or something else is going on.