Yes, this is potentially innovative, but not in the same way that the standard iPod/iPhone connector is. On iOS musical devices you can already plug them into music hardware - guitars, keyboards, mixers, etc. That's already happening.

I would actually argue that Surface Blades are not the best thing ever simply because for things like mixing you want 3 dimensional tactile feedback for subtle adjustments. Big buttons on a flat touch pad is probably better than a purely visual interface, but it seems like they are straddling the line between a non-optimal software interface for a middle ground that isn't the same as using a real mixing board, but it's maybe a bit better than using an on screen UI.

My guess is that musicians aren't going to flock to this unless they get some established producer to use it to mix some awesome beats and even then it's unclear that this is much better than a dedicated hardware device experience yet.