Is Electronics merit badge a prerequisite for Robotics?
This is a good question and one we discussed in our development group. Electronics is not likely to ever be a prerequisite for Robotics.
There are many robotics platforms that have lots of Black Boxes but are very easy to program and design with, LEGO Mindstorms and VEX for example. In the case of LEGO, a Scout would not need to know electronics.
Depending on the direction they take with their robot, Scouts could complete many of the requirements for the electronics merit badge and could do them both at the same time.