At the end of KH3 after you complete the game, the last photo you are given is this one:
No offense, but to me this picture is NOT of the light-hearted Sora we know of and are familiar with.
There is something distinctly sinister about it.
Something tells me this pic is intentional and hints at Sora's future "transformation" and that the games will likely become much darker.
What I can say, for sure, is that there is INCREDIBLY HEAVY arcane symbolism throughout the Kingdom Hearts franchise.
I'm not gonna say much more than this, but if I'm right, this story has already been told (but many don't know it) and I'm almost certain I know how Sora's story arc is gonna end.