It feels like we're fairly close yet so far. Lots of newer tools do have animation and tweening of arbitrary properties but then will just have bitmap image editors instead of a built-in vector editor for example. Or just make it really hard to tie all the stuff together.

The ease at which Flash CSx would just let you draw a circle in a spot, then click on it to get its script file and immediately add a little bit of behavior is magic for prototyping