The more I think about it, a Castlevania collection without Rondo and SoTN is so egregious. They just have to be there.
Also theorizing about a potential 3rd collection because why not.
The 1st is most likely CV1, CV3, CVII:BR, Super CV4, Chronicles, Rondo, Bloodlines, Rebirth
The 2nd may be something like CV2, SoTN, CotM, HoD, AoS, DoS, PoR, OoE
Then the third would be akin to that 'Sonic Gems' collection of 'other kinda cool or at least interesting or odd games' but not big enough to get in with the other collections:
CV 64, LoD, LoI, CoD, DxC, Judgement, Kid Dracula and Getsuu Fuma Den