>Code completion is a fundamentally harder (if not impossible) problem with dynamically typed languages, as you might need whole-program and control flow analysis to even get the types of local variables.

This pre-supposes that you don't have a test to run the program, because if you do you can just embed an interpreter in it and you have access to everything - tab completion included.

IMO This approach is partly what made IPython notebooks so spectacularly successful, and the future of dynamic language programming will look something like that.