It’s cooked and ready to serve. There are a couple of IETF process things to do, but this draft is essentially Atom 1.0. Now would be a good time for implementors to roll up their sleeves and go to work.
An Atom collection is a set of items all of the same type ("members" of the collection), where the "type" may be, for example: Atom entry, category, template, "simple resource", or any other classification of web resource.
Doesn't look like the protocol's going to be finished this month...
Tim Bray has proposed that the format might be finished, giving further exlpanation on his blog. The response on-list to this proposal certainly wasn't overwhelming approval, but consensus does seem to suggest that the missing pieces are few and that the end is very much in sight.