On https://juliahub.com/ui/Packages/General/OrderedCollections over 350 direct dependencies for this package are listed. So a breaking v2.0.0 release must be carefully coordinated in order to not wreak havoc. Ideally it would be minimally breaking, i.e. only remove a few deprecated methods, and in a way that makes it easy for most packages to support both v1.x and v2.x simultaneously to make the transition as smooth as possible.