Call of Duty: Modern Warfare 3 will feature around 20 maps but nothing is yet known if all of them will be available from start or will be featured within DLC's after the game's initial release.
Together with them, it is known that game will feature Special Ops Modes that will be based on the various survival techniques where you will have to save civilians. Special Ops mode was firstly introduced in Call of Duty: Modern Warfare 2 game. Civilian rescue missions will be Flood the Market, Invisible Threat, Wing Man, Out of Africa, No Fly Zone and Little Bro's.
It is expected that the game will feature around 12 Special Ops Modes, two of which are No Fly Zone and Radar.
To add, it seems that the newest Call of Duty game will also feature a Survival mode that will work out as a cross between Gears of War's hoard mode and zombie mode that was featured in Treyarch's Call of Duty titles. The six maps that will be available in this mode are Radar, Dome, Survival, Carbo , Seatown, Mission and Village where you will fight off hordes of armed human enemies instead of zombies.