The Mobile IPv6 mobility-management protocol enables minimum routing paths between a mobile node and a correspondent node, which may itself be mobile. This feature is called route optimization. Route optimization requires authorization of initially unacquainted and untrusted parties. A so-called return-routability procedure was integrated into the Mobile IPv6 in order to do this securely. The return-routability procedure equips the mobile node with cryptographic tokens that authenticate the mobile node and prove the mobile node's presence at a claimed new location after movement. Recently, a number of improvements or optional alternatives have been suggested to the standard procedure. The primary driver between these improvements is oftentimes further reduction of signaling messages and latency, but other improvements such as better security have also been suggested. This document discusses the potential goals for future enhancements of route optimization, the security threats that such enhancements must consider, and the various enhancement proposals and their key ideas. An evaluation of some recent proposals is included, as well as a discussion of how significant the Mobile IPv6 related optimizations are related to other ongoing optimization efforts. Finally, needs for future research are outlined.