I would give it an 8.
Reason : I don't think it will have this feature, but it would be nice to download more tunes to expand the library of tunes and patterns. I would even pay a small price for those.
Also, it would be better if you could use your Mii to track your own scores. Especially in the Workout part.
So, 8 because of lack of Mii integration and upgrades to make for even longer term playing. But, it is a solid party game, so for my uses it is great.