Great news! That really seems the next logical step to make it extendable like that - I think that's the direction Duolingo is going in for their human language learning website. Would be cool to offer beta testing of new languages to users for extra kata to get things moving.
Also you guys really need to put out the word more! I found the link by mistake, had been putting around on Codeschool, etc. for a long time and getting burnt out on the relative non-interactivity of the lessons. I had been looking for something like this for a long time and I just wish I had found it sooner!
I also have a friend who is a Python professor. I bet he'd find it useful to have his students sign up and do his exercises as part of the class. That may be another direction to go in, open it up for teachers to offer some extra interactivity to their classes!