Jun,
the categories package that Timo developed is on head now. It's not fully functional yet as it relies on some changes to core that haven't been made yet (primarily named objects, object display redirects, and noquote). However, the bulk, and essential features of the categories package should be functional already.
I cannot really judge if it is best to keep cr_keywords long term, although, my guess is that ideally we would use the new categories package for all categorization of acs objects (including everything in CR). If we did remove cr keywords we would have to migrate that data to the categories package of course. I don't think this change will make it into 5.0. It would also mean making categories part of core.
