Here is some info i just gathered for you
The game will retain mostly the same gameplay mechanics as it predecessor albeit with several changes. The weapon wheel from the first Resistance game will be returning after it was excluded from Resistance 2. There will also be new environmental objects such as chimeran plants which explode when shot at. The game will see a mixture of new and old weapons; returning weapons include the Bullseye, Magnum, Shotgun, Auger and Carbine, while one of the new weapons is the Mutator which shoots biological mists causing enemies to eventually explode causing splash damage, as well as a new grenade which is shaped like a food can which releases an arsenal of nails when it explodes.[3] All weapons are upgradeable, and become more powerful the more they are used.[3] In line with the survival theme of Resistance 3, humans are forced to assemble their weapons from whatever scrap they can gather. Frag grenades, for example, are constructed from bean cans with nails attached to them.
Multiplayer
Online competitive modes focuses on being more organized, and less clustered than that of Resistance 2. There is a co-operative mode where players can team up to play through the story mode either online or split-screen.[4] Gameinformer's podcast revealed that there will be no 8 player co-op like in Resistance 2.[5] The multiplayer maps are set in locations around the world such as the Fort Lamy prison in the Republic of Chad, Africa. Some of these maps are not included in the story mode
AND HERE IS SOME VIDEOS, NONE OF WHICH ARE MINE.
[ame=
https://www.youtube.com/watch?v=Px2VThf9D30]YouTube - Resistance 3 Gameplay Trailer[/ame]
[ame=
https://www.youtube.com/watch?v=MxJz3kBrg-8]YouTube - Resistance 3 Video Interview with Insomniac - GameInformer[/ame]
[ame=
https://www.youtube.com/watch?v=X63ayOpptL4]YouTube - Resistance 3 - Official Directors Cut VGA Trailer [HD][/ame]
And I believe its out in September