We Doubt People'll Be Complaining About More Battlefield.

The mode's called "Onslaught". Apparently it'll be playable on four maps - Valparaiso, Atacama Desert, Isla Inocentes, and Nelson Bay - with each being redesigned with new lighting, time of day and vehicles.

Apparently each map will have a different gameplay focus. No concrete details on that yet, but the update's "coming soon" apparently.

Update: The mode's coming on June 16th for PS3 players.