From the email about the changes:
- Sending and receiving messages, inviting friends, sharing the songs, playlists, and albums you are listening to, and viewing past play history.
- Mixview playback and channel playlists.
- Apps for Zune HD.
- Purchasing music videos or streaming them as a part of Zune Music Pass from the Zune PC software.
- Re-downloading, re-activating, or re-licensing previously purchased music videos if / when you upgrade your PC
Microsoft are also keen to stress that one of the unsung gems of Windows Phone, the Zune Music Pass, will not be affected by this change.
A number of the features are likely to re-surface in Xbox Music (such as the social network features) but other areas of the Zune Desktop will not be returning. Much like the removal of the Apps section from the Desktop App, I suspect that the areas being tweaked are very rarely used by the majority of users, and can be better accommodated through other means.