Graphical programming would be a 'killer app' for any language that can implement it first. Reasoning about code visually will not only make programming more accessible, but it will allow us to apply spatial reasoning skills to the task of writing applications. Flow-based programming seems to have the best chance of getting this sort of thing off the ground: http://www.jpaulmorrison.com/fbp/
Sorry to sour your future-casting, but this "killer app" has been a non-starter for many many years. Except for some niches where the flow of data is the primary thing you want to express, visual languages are too cumbersome. See http://en.wikipedia.org/wiki/Visual_programming_language
For a graphically based programming concept that webpage is curiously wanting of graphical examples...
Ideally I'd like something that one could insert into an existing language, so that it would gain usage quickly. (I'm betraying certain intentions already...)
