Would make more sense to get his “non-yami” version in DSOD. He was more prominent in the movie, plus I don’t see them going back and making a new LD for DM. It’s been well over a year since we got a character for that world.
According to event archives, they first become unlockable in May of 2019 in the Tag Duel tournament. I remember that, because right after, players were abusing their pre-nerfed skill Masked Tribute in Subterror decks back then.
I got my hopes up for Ryou Bakura because of that dialogue ... but is that our only hint ? No dev mentions the line of duelists they plan to release and when ? XD
Though probably knowing and waiting would take away from the joy of the surprise