MichaelBay.com has revealed that China's Han Geng has joined the cast of Transformers 4. According to the site:

He’s one of Asia’s top stars in the worlds of music, television and movies and has become one of the most influential entertainers in China.

Now he’ll also be known for Transformers 4. Welcome Han Geng to the cast of Transformers 4. – Michael Bay

The question of exactly how much of a role China and these actors will play in the movie remains unknown. Thanks to Wynton R. for the info.