This is the first official word that Transformers is getting the trilogy treatment, although it really comes as no surprise. But Paramount cautions that nothing is set in stone yet -- they merely wanted to stake their claim on the date. There's currently no direct competition, and the arrival of giant robots pretty much means there won't be.
The studios wouldn't confirm whether Michael Bay, Shia LaBeouf, and Megan Fox would return for number three, though Bay seems likely. However, LaBeouf and Fox are busy filling up their slates with John Grisham thrillers and Fathom adaptations, so we could see one or both of them drop out of the franchise. And would it matter terribly if they did? Does anyone really go to a Transformers movie for the human players and not the giant robots?
So, barring any other official word, here's where you can express your pleasure, speculate as to what a third installment would center on, whether Revenge of the Fallen will end on a major cliffhanger, and hope fervently that Megan Fox returns. It's just a guess, but I suspect she's almost as much of a draw as Optimus Prime.