New details on Gears of War 3 were brought to light recently by a translation from a feature article in a Russian magazine. Some of the main points discussed in the article include the addition of mech suits, new guns, and a little bit of story details.
These new mech suits, which are a first in the Gears of War series, will be heavily armoured in the front with machine guns and grenade launchers equipped to fight off enemies. The armoured suits will also be able to fold out into a stationary turret with shields for nearby soldiers to take cover behind.
There are also some new guns which include the ability to shoot grenades under the ground to blow enemies away from behind their cover, as well as a special new machine gun that will become more powerful as players fire it.
The translation is a little rough but it does sum up the article fairly well. There are also story details that step into spoiler territory for those who haven't completed the previous titles, but you can go to the translation for those who want to get into that territory.
Source: Epic Forums