There are currently a number of
Sequence-related proposals that are marked with "Awaiting Review" but haven't gone through review yet.
My best bet is that most of these proposals will have to be rewritten using opaque result types. If this is the case, then most of these proposals also need a feature that allows the addition of conditional constraints on an opaque result type's
associatedtypes, delaying their review further.
Can we get an official roadmap from the core team for the future direction of
Collection? This way (future) proposal writers can avoid doing any unnecessary work.