There are clearly lots of parts of the Hollow Earth yet to be explored, which means plenty of new creatures to be introduced, and certainly one of those could be the offspring of Kong. How that offspring comes into being, given that Kong seems to be the last of his race at this point, will remain a mystery for now — but since the entire Hollow Earth mythology isn’t exactly out of the pages of Scientific American, we’re confident that the filmmakers will come up with some of kind of word salad to explain it all.
Kong could end up discovering another of his kind — a female — hidden deep within Hollow Earth, perhaps waiting for his return or the arrival of another of their species. The birth of Kong’s son could be the big moment that the movie leads up to, with other dangerous creatures all attempting to stop that from happening for reasons of their own.
An alternate twist would be to have the Kong we know from this movie and Kong: Skull Island actually be the “son” of the title, and have him discover that his much bigger, much meaner dad has secretly been surviving all along in Hollow Earth. That would perhaps set up some massive (in all senses of the word) daddy issues for Kong Jr., and we know how much screenwriters love to delve into those.
One opportunity that a Kong-centric movie does provide is the chance for Legendary to create a whole new roster of original monsters. Since Kong has had far fewer film appearances than Godzilla, with the latter ruling an extensive Japanese shared universe for 60 years before this MonsterVerse launched, the big ape has had far less opportunities to develop a monstrous rogues gallery of his own. Son of Kong or whatever it ends up being called could build upon the foundations for that which were put down in Kong: Skull Island and GvK, without having to cut Toho Studios a check to use one of their babies.
Speaking of which… where does Godzilla fit into this whole scenario? We last saw the big dragon swimming peacefully back into the deep after he and Kong teamed up to defeat Mechagodzilla. Is there room for him in Son of Kong, or will he potentially get another solo movie of his own?
If he does, as we mentioned above, there are plenty of opponents to choose from should Legendary want to pay the (reportedly exorbitant) licensing fees that Toho requires. As our David Crow points out here, kaiju from the past 30 years alone like Biollante and Destoroyah rank among Godzilla’s most compelling adversaries, and even oldies such as Hedorah, Gigan or Kumonga could be reinvented as more modern enemies. And there’s always the possibility of Mothra or King Ghidorah returning as well.