As with many carriers jumping on the "I'm ready!" train, O2 DE has said on the interwebs that they are indeed ready to push the Mango update to customers. They're now awaiting Microsoft's green light. While Deutsche Telekom is able to provide an actual handset roadmap and status per manufacturer, O2 has unfortunately not provided any further detail as to when.

Source: @o2de, via: WP7App.de