Protection of user privacy will gain increasing importance in future mobile systems. To meet the users' privacy needs the approach to reveal different amounts of personal data under several different pseudonyms is promising. This approach can still be undermined with application knowledge as well as with information originating from the communication process itself. Here, mobility management plays a central role as it reflects the user's behavior. Thus, the approach of multiple pseudonyms can only be successful if the communication system is designed for it. In this paper, the respective threats resulting from IP-based mobility management are analyzed. As existing proposals do not protect against these threats, a new approach to mobility management protecting multiple pseudonyms is outlined.