Harlem Désir's days as head of the PS were clearly numbered after the municipal election fiasco, but to kick him upstairs to European Affairs to get rid of him is not a good move. Yes, Jouyet will be calling the shots from the Elysée, but relations with the EU are crucial, and Désir is a novice in this area (and didn't demonstrate much skill as party leader either).
Cambadélis is an apparatchik, so he'll be right at home at Solférino. The question is how to rebuild the party. If Camba has any ideas about how to do this, I don't know what they are.