Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. Minimize dependencies, keep it fast, and keep it portable.
The tools of ROS should be easy to use and adopt for controlling diverse robotics hardware from diverse computing systems. Users and developers should control ROS systems, not the other way around.
Fault tolerance and long-duration reliability must be at the forefront of any ROS system controlling real hardware. ROS can and should help users design systems that scale, self-heal, and run forever.