Entertainment site Vulture
reports that their inside sources close to the Transformers 4 production team are informing them that Transformers 4 may film in China, and may even be co-produced between Michael Bay's production company and a Chinese partner company. The basis of the report is an increasing desire for US made films to make it in the notoriously tough Chinese box office. The article also includes a statement from Paramount, stating that "the script is still being written" and "it is not a Chinese co-production", so make of it all what you will.
It's not impossible that China may be involved in Transformers 4 in some way - after all, we have reports that London may have some location filming and that Bangkok is being considered. For now, take this as a rumor - albeit one that would make good financial sense should it play out.