Ref dandi/dandi-schema#143 and motivation I have expressed yesterday in our dandi-standup - to be able to discover which dandisets became public from first being embargoed. Going through dandisets which have embargoedUntil set would provide an indirect answer. Also IMHO it would be more factually correct than e.g. some hypothetical date user or us set in metadata while provisionally planning the study: seeing some future date for unembargo in a public dataset would be pretty much incorrect metadata IMHO.