They might still be getting around to it. After they take a break from doing their lifeless pachislots that is.
They better lol. I just don't get this logic Nintnendo has: "We're starting the GB VC, what are some popular games we can put on here? Three Castlevania games are for the GB, and one of them is universally panned, while the one other is a classic and the other is OKly received... It makes more sense to put the most hated one on here, call Kopachi now!!"
From what I understand Nintendo contacts the original publisher and gets the license to release it I the VC. Idk if publishers approach Nintendo on their titles being available, but either way having the Adventure alone makes zero sense. Ik Belmonts revenge is the sequel, but releasing that first would've meant a WAY more popular game would be available. Even Legends would do OK on VC I imagine with its fucking rediculous price online plus the curiosity of fans who haven't played it.