Happy to know this kickoff. 
Per my experience of using ROS Navigation Stack, I would like to add below items into the wish list:
- make a more flexible mechanism for plugin implementations, especially for recovery plugins.
- Support multi-thread and heterogeneous computing
- Adopt AI gene (e.g. Reinforcement learning) into path planning and collision avoidance.
- Support more map types
- it’s better to support 3D path planning and CA