Today is the day Helldivers 2 achieved a higher Steam CCU than the F2P part of Halo: Infinite.
Some extra coop-ish shooters as reference:
PUBG 3,257,248 (now F2P)
Counter-Strike GO/2 1,818,773 (F2P)
Apex Legends 624,473 (F2P)
Call of Duty 491,670
Counter-Strike 319,586 (F2P)
Destiny 2 316,750 (F2P)
Helldivers II 276,364
Dying Light 2 274,983
Halo Infinite 272,586 (F2P)
Team Fortress 2 253,997 (F2P)
Payday 2 247,709
The Finals 242,619 (F2P)
Rainbow Six Siege 201,053
Warframe 189,837 (F2P)
Left 4 Dead 2 162,399
Halo MCC 161,024
Outriders 125,143
Borderlands 2 124,678
Insurgency 121,575
Battlefield V 116,104
The Division 114,228
Remnant II 110,856
Warhammer 40,000 Darktide 108,395
Battlefield 2042 107,376
Warhammer Vermintide 2 104,323
Borderlands 3 93,820
Payday 3 77,938
Killing Floor 2 69,987
Battlefield 1 53,714
Payday 50,316
Deep Rock Galactic 46,687
Left 4 Dead 30,616
Vermintide 24,700
Killing Floor 24,107
Borderlands 23,655
Battlefield: Bad Company 2 21,923
Battlefield 4 12,425
Star Wars Battlefront II 10,489
Battlefield 3 1,412
Battlefield 2 1,399
Star Wars Battlefront 623
Battlefield Hardline 279
Helldivers II achieved a higher all time Steam CCU peak than the whole catalog from PS Studios, Microsoft Game Studios, Activision, Bethesda, EA, 2K, Rockstar, Ubisoft, Valve, WB, Bandai Namco, Square Enix, Capcom, Sega, Koei Tecmo, Techland, Embracer with only these following exceptions:
Counter-Strike GO/2 (1,818,773, F2P)
Dota 2 (1,295,114, F2P)
Elden Ring (953,426)
Hogwarts Legacy (879,308)
CoD (491,670)
Fallout 4 (472,962)
Life is Strange 2 (468,717)
GTAV (364,548)
Starfield (330,723)
Counter-Strike (319,586, F2P)
Skyrim (287,411)
These are the all time Steam CCU peak for the Sony PS Studios games released on PC:
Helldivers II 276,364
God of War: 73,529
Spider-Man Remastered: 66,436
Horizon Zero Dawn: 56,557
TLOU Part I: 36,496
Days Gone: 27,450
Spider-Man Miles Morales: 13,539
Uncharted collection: 10,851
Ratchet Rift Apart: 8,757
Detroit: 8,222
Helldivers 1: 6,744
Death Stranding: 6,093
Guns Up!: 2,277
Journey: 1,757
Predator Hunting Grounds: 1,504
Beyond Two Souls: 1,346
Heavy Rain: 747
Sackboy: 610
Everybody's Gone to the Rapture: 191
What's the predicted player fall off by mid march? 4-6 weeks post launch are often the markers of staying power vs FOMO.
Around that time they will have the remaining important bugs (the matchmaking) fixed, a great amount of great reviews in the media, the user ratings in Steam very improved compared to now and I assume they'll have published the first post launch Warbond/extra unlockables.
So I think they will have passed their peak, which I think will be at around 400-450K aprox. and then will have came down at 300K peak per weekend.