As of https://cordova.apache.org/announcements/2015/04/21/plugins-release-and-move-to-npm.html, new plugins should be published in npm and old ones migrated to npm.
The question is, once migrated our plugins to npm, should we keep publishing plugins via plugman publish (update migrated ones or new plugins) besides npm publish? If yes, how long?
The Cordova plugins registry has now been made immutable - use npm is the way forwards.