A few days ago, a photo was taken of two dark colored vehicles on the back of a trailer close to the Transformers 4 set in Texas. One of them appeared to be a NEST vehicle, but the vehicle on the back of the trailer was hard to identify. According to some other reports, it appears to be a Rally Fighter, a vehicle used for off-road driving and racing. The paint scheme makes me believe that this is a Decepticon. On top of that, fans that live in the area have said that they have seen the Rally Fighter pursuing Bumblebee. The below photo is not from the TF4 set.
Also, TJ Miller has tweeted out a couple of photos from the Transformers 4 set in a Texas house, which is presumably the house of Flynn Vincent (Mark Wahlberg) and his daughter (Nicola Peltz). They are meant to be humorous (he called them exclusive on-set photos) and don't mean anything, but it's nice to be seeing some on-set photos nonetheless.