Yes­ter­day Para­mount and Dream­works offi­cially announced that Trans­form­ers 3 shall be land­ing in cin­e­mas come Fri­day July 1st 2011, Vari­ety:

Para­mount and Dream­Works are forg­ing ahead with “Trans­form­ers 3,” dat­ing the movie for release on July 1, 2011.
It’s the first word of the three-quel, although Para­mount insid­ers down­played the impor­tance of the move.
They said the stu­dio wanted to claim the date before a com­peti­tor did, con­sid­er­ing that the 2011 sum­mer release cal­en­dar is fill­ing up.
No deals have been inked with direc­tor Michael Bay or fran­chise stars Shia LaBeouf and Megan Fox. Nor has a writer been hired for the third installment.

In response, Michael Bay has posted on his forums:

I said I was tak­ing off a year from Trans­form­ers. Para­mount made a mis­take in dat­ing Trans­form­ers 3 — they asked me on the phone — I said yes to July 4 — but for 2012 — whoops! Not 2011!!! That would mean I would have to start prep in Sep­tem­ber. No way. My brain needs a break from fight­ing robots.

Michael

Looks like some­one messed up here. No date set for now — but we know Trans­form­ers 3 is def­i­nitely planned.