Actually that's not the best thing we can hope for. Iga has bloodstained with already a huge fan base. It would be a waste of money and a backwards move for him to buy Castlevania after creating such a buzz for his own IP. Besides, there have been plenty enough Iga Castlevania games.
The best thing for Castlevania would be a new dev who gets the game and knows how to make an awesome 2d platformer. I vote vanillaware.
I agree with your first statement. IGA now has his own franchise, with complete creative control. He can work with that from now on. It's his baby. CV will always hold a place in his heart, but I don't think it'll ever be as big as Bloodstained could possibly be, since Bloodstained is HIS.
As for CV, I don't really agree with VanillaWare. Granted, I've only played two of their games (Muramasa Rebirth and Dragon's Crown). I just don't feel they'll do it justice. None of their games have ever screamed Castlevania to me.
WayForward is definitely a good group to look toward, as they haven't yet disappointed me with a game (though I heard their 3D games are atrocious). Or even the group who made the old Metroid games. We can all guess why they'd be good (and why it'd never happen, lol).