Well, I wasn't thinking on replacing the actual programming structure and language, what I ment is that a graphical object oriented programming could be a cool feature for people that needs to do simple stuff and don't want to get that far intro code programming.
It's not really replacing... it's adding another layer on top of it. And as with all other layers that Arduino has, comes an overhead and implementation details that get hidden from the user (which is what you want), but it will remove functionality because the graphical blocks will do what the designer wanted, and if it's not exactly what you want, you're stuck again.
Plus, for simple stuff you can go through the examples and copy/paste together a solution for your problem. It's not hard, it just looks hard. Try using a flow-chart to design what you need, and then transpose that to paper using the basic operators like if(), while(), for(;;), etc... in no time you'll see how you don't need the graphical user interface.
If that is a necessity, you can always go with Functional Block Description (I see this in Siemens PLCs), but I don't think you'll like the cost...