ShowBlitz says

EXCLUSIVE: Paramount and Hasbro were so fond of the $1 billion that “Transformers: Dark of the Moon” made worldwide that they're going for two: plans are being considered to shoot the fourth and fifth installments back-to-back, Variety's Justin Kroll and Marc Graser report. Hasbro said on a Monday earnings call that it was in "active discussions" with Paramount, Michael Bay and Steven Spielberg on how to move forward, and sources close to the planning process tell SHOWBLITZ it could actually be two films headed into production, a measure that can save millions because cast and crew deals only be negotiated once, among other factors. (Cinema, Jason Statham, Transformers 4, Transformers 5)