I'll say it a million and one times, it really should have happened after AU and VST3 were rolled out 15 years ago.
Think of how every change from Apple and Microsoft, to 32 to 64 etc. all of it would have had easily coded transitions to alleviate missing plugins etc. Imagine a world where only the laziest of developers would cause a version upgrade to force you to include say Kontakt 4 in your modern setup for that old song with Kontakt 4 in it.