Ok, it seems that everyone is getting confused over this so let me try and offer some understanding on the situation from today's announcement.
Halo CE (Port of Original Engine) 19 Maps (No Forge Likely);
Battle Creek
Blood Gulch
Boarding Action
Chill Out
Chiron TL-34
Damnation
Danger Canyon
Death Island
Derelict
Gephyrophobia
Hang 'Em High
Ice Fields
Infinity
Longest
Prisoner
Rat Race
Sidewinder
Timberland
Wizard
Halo 2 (Port of Original Engine) 23 Maps (No Forge Likely);
Ascension
Backwash
Beaver Creek
Burial Mounds
Coagulation
Colossus
Desolation
Elongation
Foundation
Gemini
Headlong
Ivory Tower
Lockout
Midship
Relic
Sanctuary
Terminal
Tombstone
Turf
Uplift
Warlock
Waterworks
Zanzibar
Halo 2 Anniversary (Brand New Engine) 6 Maps (Forge Possible);
Ascension Anniversary
Unknown
Unknown
Unknown
Unknown
Unknown
Halo 3 (Port of Original Engine) 24 Maps (Forge Likely);
Assembly
Avalanche
Blackout
Citadel
Cold Storage
Construct
Epitaph
Foundry
Ghost Town
Guardian
Heretic
High Ground
Isolation
Last Resort
Longshore
Narrows
Orbital
Rat's Nest
Sandbox
Sandtrap
Snowbound
Standoff
The Pit
Valhalla
Halo 4 (Port of Original Engine) 28 Maps (Forge Likely);
Abandon
Adrift
Complex
Daybreak
Erosion
(Ascent)
Exile
Forge Island
Harvest
Haven
Impact
(Relay)
Landfall
Longbow
Meltdown
Monolith
Outcast
Peridition
Pitfall
Ragnarok
Ravine
(Settler)
Shatter
Skyline
Solace
Vertigo
Vortex
Wreckage
Total Map Count: 100
Hopefully this improves understanding on a potentially confusing situation
Halo CE (Port of Original Engine) 19 Maps (No Forge Likely);
Battle Creek
Blood Gulch
Boarding Action
Chill Out
Chiron TL-34
Damnation
Danger Canyon
Death Island
Derelict
Gephyrophobia
Hang 'Em High
Ice Fields
Infinity
Longest
Prisoner
Rat Race
Sidewinder
Timberland
Wizard
Halo 2 (Port of Original Engine) 23 Maps (No Forge Likely);
Ascension
Backwash
Beaver Creek
Burial Mounds
Coagulation
Colossus
Desolation
Elongation
Foundation
Gemini
Headlong
Ivory Tower
Lockout
Midship
Relic
Sanctuary
Terminal
Tombstone
Turf
Uplift
Warlock
Waterworks
Zanzibar
Halo 2 Anniversary (Brand New Engine) 6 Maps (Forge Possible);
Ascension Anniversary
Unknown
Unknown
Unknown
Unknown
Unknown
Halo 3 (Port of Original Engine) 24 Maps (Forge Likely);
Assembly
Avalanche
Blackout
Citadel
Cold Storage
Construct
Epitaph
Foundry
Ghost Town
Guardian
Heretic
High Ground
Isolation
Last Resort
Longshore
Narrows
Orbital
Rat's Nest
Sandbox
Sandtrap
Snowbound
Standoff
The Pit
Valhalla
Halo 4 (Port of Original Engine) 28 Maps (Forge Likely);
Abandon
Adrift
Complex
Daybreak
Erosion
(Ascent)
Exile
Forge Island
Harvest
Haven
Impact
(Relay)
Landfall
Longbow
Meltdown
Monolith
Outcast
Peridition
Pitfall
Ragnarok
Ravine
(Settler)
Shatter
Skyline
Solace
Vertigo
Vortex
Wreckage
Total Map Count: 100
Hopefully this improves understanding on a potentially confusing situation