I would love to see some unknown, young japanese dude/dudette within Konami step up and take the torch for this series. I still don't believe that Mercury Steam is gonna make more than maybe 1-2 more Castlevania games, and then what?
I'm confident that the series will find its way back to Japan sooner or later. And I also think that the Metroidvania formula WILL be revisited, albeit with some tweaks. I've given up on WayForward cause they're making all sorts of Castlevaniaesque games (Bloodrayne and Aliens Infestation to a lesser extent) but I don't think they'll ever be given a shot at the real thing.
It's really up to Konami. If the sequel to Lords of Shadow doesn't sell as much as LoS (which it probably won't) I doubt Konami is gonna put tons of money into this "God of Warlevania" formula anymore. I do however believe that the next game from Mercury Steam will have a bigger budget than LoS, possibly the biggest in the history of Castlevania. It's both scary and exciting.,,