Jolin posted this today on her Weibo.

[練舞魯 黑髮尤物!!!!!

9月27日 18:45]

It means that she's practicing a choreography for Black-haired beautiful girl!!
So Black-haired beautiful girl might actually be the Hydron MV*!
In that case the Chinese 30s preview we had before was just a CF for China's Got Talent and nothing else...

*: Hydron made events in China.
One person has been chosen from each 8 cities where the event was held and these people are going to be sent to Taiwan to shoot an MV from Jolin's new album!