New images show various Transformer cars, including a maybe new one, showing up in the country to prep for around a month's worth of filming. The cars spotted in China are Bumblebee (2014 Camaro), Hound, Corvette Stingray, Bugatti, Pagani Huayra and a new red vehicle identified as a 2014 Ferrari 458 Italia Speciale (left pic).
In Dark of the Moon, the Transformers called "Dino" (or Mirage) was also a 458 Italia but I would be surprised if that character returned considering his near non-existent part in the last film. Also the car looks too much like the Pagani (right pic) to a non-car aficionado like me and most movie goers. The range in vehicle colors is no accident as it is a design choice to make it so requires only a glance for viewers to know what character they are looking at regardless of the make and model of the alt mode. The addition breaks that formula so guessing it serves some other purpose than a TF alt mode. It is also possible the car arrived on the same ship (or plane) as the other vehicles but has nothing to do with TF4 production.
Xinhuanet.com, Age of Extinction will spend the last two weeks of October filming in multiple areas including Tsing Ma Bridge, Lyndhurst Terrace, Central, Bank of China Tower, Victoria Harbour , Hong Kong Convention and Exhibition Centre, Sham Shui Po, Kowloon and Legislative Council Square. There is a mention of some plot points but the Google translations mangles it so it reads "Mark Wahlberg finally say goodbye to her daughter TOUGH intestinal and Hornet commissioned to send their daughters to a safe location, a congregation will immediately robots Autobots battling the forces of evil." The suggestion is a big battle scene will be filmed around the Convention Center but not really sure.
Michael Bay is supposed to arrive in the country soon to start the filming. Based on the variety of locations, the lack of the main cast, short time window and large volume of "China" being filmed in the United States, everything about this screams "2nd unit production." While there might be pyrotechnics going off here and there, I get the impression he is really there to give the China portion of filming more legitimacy as part of the "cooperation agreement" between China and Paramount Pictures. An agreement designed to give TF4 a favored release date next summer and help with promoting the movie in the country.
Update: It looks like I was wrong about the cast not showing up as they have been spotted arriving to Hong Kong. So far only have confirmation of Nicola Peltz, Mark Wahlberg, and Sophia Myles. Since Myles has not been spotted without Stanley Tucci nearby. Jack Raynor is also in China as proven by image thanks to Mawii Y.