Despite having not yet debuted in the rebooted Mortal Kombat movie series, Johnny Cage's backstory has already been set up for a major change when he arrives in Mortal Kombat 2. That's thanks to how Simon McQuoid's reboot ends as well as the established logic of champions in the new MK timeline. When Cole Young eventually recruits Johnny Cage, he might be recognizable, but his story probably won't be.
According to the lore of Mortal Kombat, tournaments happen once every generation (50 years), and since the movie confirms outright that Shang Tsung used Sub-Zero to cheat his way to victory in the previous nine, there's an established timeline of 450 years. Sub-Zero's method of cheating is to kill off the previous Earthrealm champions before a tournament even takes place, which makes the succession of future champions complex. Either each generation spontaneously generates new champions, or all surviving champions were descendants of Scorpion's son. And then there's the issue of Acana powers, which limit the possibility of champions learning to become champions without a dragon symbol.
Either way, that makes Johnny Cage's original lore backstory impossible. In the games, Cage descended from a Mediterranean cult that bred warriors with special superhuman abilities for the gods. The fact that Sub-Zero wiped out previous champions over the course of 450 years makes the endurance of Cage's bloodline improbable - if they were champions and he was born with the MK mark, Sub-Zero overlooked them, which simply doesn't work because they would have been recruited to fight or hunted. So, logically, Cage can only be a champion if he previously killed another champion or he too is a descendant of Scorpion.
It wouldn't be unreasonable for Scorpion's son to have bred lots of potential champions, but in order for Cole Young to be unaware of his status as a champion or even the lore behind his birthmark, the whole bloodline has to have been kept secret. Otherwise Sub-Zero would have been able to hunt them down and kill them off, seeking to stop the chance of the prophecy coming true, and Sub-Zero himself says he has no reason to suspect the bloodline endures in Mortal Kombat. The alternative of Cage killing someone to take their mark doesn't really fit the backstory of a Hollywood actor either, which suggests the most likely solution is that of the creation of spontaneous champions each generation by the Elder Gods.
Unfortunately, that still wipes out Cage's backstory as a descendant of the superhuman cult, because of Sub-Zero's work defeating (i.e. killing) the Earthrealm champions of previous generations. Cage, like Cole Young, probably has to be a Chosen One without fully realizing the weight of legacy behind him because the alternative option of a faithful adaptation of his Mortal Kombat backstory would make his existence impossible. His ancestors would have been on Sub-Zero's hitlist (just as Cage himself would have been as a known champion in 2021's timeline, no doubt). On top of that, in the games, Cage learns his powers thanks to his ancestry, but the Arcana magic tied to being a champion changes that element of his history too. So while fans may be excited at the prospect of getting Johnny Cage in Mortal Kombat 2, it seems inevitable that he has to be a new version.