Call of Duty: Modern Warfare is set to launch on PS4, Xbox One, and PC by the end of this month, yet we still do not have a confirmed director of multiplayer maps that will be accessible at launch.
Unfortunately, we still do not have official word on what maps will be usable at launch. However, we may understand what the game will come packing at launch, map wise, appreciation to a new leak.
Said leak comes the way of YouTuber TheGamingRevolution, who has, largely, been a very reliable source when it reaches to Call of Duty: Modern Warfare leaks.
As per the YouTuber, there will be triple maps for Ground War, seven for Gunfight, and 10 classic multiplayer maps.
So, through all three modes, there will be 20 maps in the game at blastoff, which is aa reasonable number but is not as big as some previous rumors implied it would be.
Nonetheless, below you can see a breakdown of all the maps that are available in the game, governed by the aforementioned three categories.

Conventional Multiplayer Maps:
Aniyah Palace
Cave
Cave (Night)
Deadzone
Euphrates Bridge
Hackney Yard
Hackney Yard (Night)
Grania Raid
Gun Runner
Gun Runner (Night)
Piccadilly
Petrograd
Spear
Spear (Night)
Ground War Maps:
Downtown Donetsk
Farms
Karst River Quarry
Gunfight Maps:
Docks
Hill
King
King (Night)
Pine
Showers
Speedball
Stack
Of course, all of this map schedule should be taken with aa seed of salt, like any unofficial evidence. As mentioned already, the source here has been pleasantly reliable in the past, but only authorized information is worth carrying to the bank.
And unfortunately, it does not seem like Activision is going to give us authorized information on the maps in the game until release.
Call of Duty: Modern Warfare will be accessible for PS4, Xbox One, and PC when it launches in a few weeks on October 25. It will be priced at $60, and be available in a mixture of editions.