You can draw your own conclusions from the list below! I think Marko's source is off on J704, which seems sure to be M5 MacBook Pro 14" if the patterns hold, which is his whole premise. As you can see, I believe it will be Mac17,2. The "Mac" firmware identifiers (e.g., "Mac17,1") vary in ways that aren't really predictable, but you get the idea.
As you can see, my prediction for the fifth generation leaves open the possibility that the iMac and the base Mini won't get M5 (the tilde ~ in front means it's not on Marko's list), but if they do, then those are likely to be the Apple silicon "J" identifiers for them.
Finally, take note -- the lede is buried here -- those Apple silicon "K" identifiers are the first of their kind. That's got to be a something big, like a redesign for the Apple-silicon MacBook Pro?
First generation
J273 = A12Z Mac mini
J274 = M1 Mac mini
J293 = M1 MacBook Pro 13"
J313 = M1 MacBook Air
J314s = M1 Pro MacBook Pro 14"
J314c = M1 Max MacBook Pro 14"
J316s = M1 Pro MacBook Pro 16"
J316c = M1 Max MacBook Pro 16"
J456 = M1 iMac (Two ports)
J457 = M1 iMac (Four ports)
J375c = Mac13,1 :: M1 Max Mac Studio
J375d = Mac13,2 :: M1 Ultra Mac Studio
Second generation
J413 = Mac14,2 :: M2 MacBook Air 13"
J415 = Mac14,15 :: M2 MacBook Air 15"
J473 = Mac14,3 :: M2 Mac mini
J474s = Mac14,12 :: M2 Pro Mac mini
J414s = Mac14,5 :: M2 Pro MacBook Pro 14"
J414c = Mac14,9 :: M2 Max MacBook Pro 14"
J416s = Mac14,6 :: M2 Pro MacBook Pro 16"
J416c = Mac14,10 :: M2 Max MacBook Pro 16"
J493 = Mac14,7 :: M2 MacBook Pro 13"
J180d = Mac14,8 :: M2 Ultra Mac Pro
J475c = Mac14,13 :: M2 Max Mac Studio
J475d = Mac14,14 :: M2 Ultra Mac Studio
Third generation
J504 = Mac15,3 :: M3 MacBook Pro 14"
J433 = Mac15,4 :: M3 iMac (Two ports)
J434 = Mac15,5 :: M3 iMac (Four ports)
J514s = Mac15,6 :: M3 Pro MacBook Pro 14"
J514c = Mac15,8 :: M3 Max (14/30) MacBook Pro 14"
J514m = Mac15,10 :: M3 Max (16/40) MacBook Pro 14"
J516s = Mac15,7 :: M3 Pro MacBook Pro 16"
J516c = Mac15,9 :: M3 Max (14/30) MacBook Pro 16"
J516m = Mac15,11 :: M3 Max (16/40) MacBook Pro 16"
J613 = Mac15,12 :: M3 MacBook Air 13"
J615 = Mac15,13 :: M3 MacBook Air 15"
J575d = Mac15,14 :: M3 Ultra Mac Studio
Fourth generation
J604 = Mac16,1 :: M4 MacBook Pro 14"
J623 = Mac16,2 :: M4 iMac (Two ports)
J624 = Mac16,3 :: M4 iMac (Four ports)
J614s = Mac16,8 :: M4 Pro MacBook Pro 14"
J614c = Mac16,6 :: M4 Max MacBook Pro 14"
J616s = Mac16,7 :: M4 Pro MacBook Pro 16"
J616c = Mac16,5 :: M4 Max MacBook Pro 16"
J575c = Mac16,9 :: M4 Max Mac Studio
J773g = Mac16,10 :: M4 Mac mini
J773s = Mac16,11 :: M4 Pro Mac mini
J713 = Mac16,12 :: M4 MacBook Air 13"
J715 = Mac16,13 :: M4 MacBook Air 15"
Fifth generation (projected)
J700 = Mac17,1 :: A18 Pro MacBook 12"
J704 = Mac 17,2 :: M5 MacBook Pro 14"
~J723 = Mac17,3 :: M5 iMac 24" (Two ports)
~J724 = Mac17,4 :: M5 iMac 24" (Four ports)
J714s = Mac17,5 :: M5 Pro MacBook Pro 14"
J714c = Mac17,7 :: M5 Max MacBook Pro 14"
J716s = Mac17,6 :: M5 Pro MacBook Pro 16"
J716c = Mac17,8 :: M5 Max MacBook Pro 16"
J775c = Mac17,9 :: M5 Max Mac Studio
J775d = Mac17,10 :: M5 Ultra Mac Studio
J813 = Mac17,11 :: M5 MacBook Air 13"
J815 = Mac17,12 :: M5 MacBook Air 15"
~J873g = Mac17,13 :: M5 Mac mini
J873s = Mac17,14 :: M5 Pro Mac mini
J833ct = Mac17,15 :: Mac Pro? iMac Pro?
Sixth generation (projected)
J804 = Mac 18,1 :: M6 MacBook Pro 14"
K114s = Mac 18,5 :: M6 Pro MacBook Pro 14"
K114c = Mac 18,7 :: M6 Max MacBook Pro 14"
K116s = Mac 18,6 :: M6 Pro MacBook Pro 16"
K116c = Mac 18,8 :: M6 Max MacBook Pro 16"