I imagine the popularity of cheap 'steam key only' bundles has a lot to do with the 15% increase in active users. It might also account for the big increases in secondary Brazilian and Russian markets as well.
Overall, I like the idea that Steam isn't resting on its laurels. There seems to be a willingness to try new things and dispense with systems that don't work. Not many huge corporations do it, so I give them props for that.
Still, this new system that's being suggested sounds really, really messy to me. There isn't enough information, though...