The first official poster of Ice Age 3 has been shown at Showest, a convention for themovie industry. Thanks to Worstpreviews we may see this Ice Age 3 poster in quite good quality (not hi-def because it's actually a photo of the poster):
(Click on the poster to enlarge it.)
Ice Age 3
Dawn of the Dinosaurs
So now as a result we also have a full title for Ice Age 3: it would be Ice Age: Dawn of the Dinosaurs.
The title is kind of cryptic alone because dinosaurs were long extinct before mammals like Manny the mammoth, Sid the ground sloth or Diego the smilodon have ever existed...
Two hypothesis may be made then: either our friends from the Ice Age are traveling back to the past of Earth, or they found a remote valley where the dangerous reptiles are still living...
I would bet on the first one. But I would be glad if there is a more subtle trick in Ice Age 3 synopsis.