I also disagree with the sentiment that CV wouldn't need a "major overhaul".
What should happen to the series in my opinion right now is either:
A) Super Steroidvania: The Comeback
Basically the CV we know and love, on steroids. Play it safe - make a 2/2.5D side scrolling action platformer, and perfect it. Make it HD, with some gorgeous hand-drawn graphics that would make Secret of Mana cry in shame. Roid up the platforming - look at Super Meat Boy and all the cool 2D platformers recently released, and make it an intense experience. I'm talking about a toolset and level design that allows us to see Hans-Axel Belmont running then sprinting then sliding under a collapsing roof only to roll and jump and grab to the opposite wall with his chain then pulling in and sliding down the wall only to backflip in a closeby opening. Nonstop. For hours.
Take the combat and make it FINALLY exciting - put in parries and dodges and combos and build in a 2D version of a Kamiya game. Let us juggle enemies and throw them into other ones with our chain, let us parry and counterattack, backflip behind mobs and use 5 different, input based moves for each subweapon. I'm talking about being able to throw your daggers at mobs, using them after a timed dodge to stab a monster in the eyes and stun him, throw them at weak points to build temporary grappling points for our yet unupgraded whip, throwing them during a jump to pin a monster in place for a few seconds and so on. Take a cue from MS and build context sensitive moves - whip grab a small enemy and pull him to yourself or throw him on someone else, or whip grab a boss and pull yourself in for a kick in its ugly face.
There's an UNIVERSE of things to do with 2D sidescrollers. They could take the classic formula and amp it up in hundreds of ways. Get rid of whoever thinks that reusing assets and changing the magic subsystem makes each game unique, and rebuild the legend from scratch.
B) Streets of Vania, aka The Legend of Vania: A Belmont for the Future, aka Red Dead Vania
Plan B: screw sidescrollers. 20 years of Castlevania, was a great ride, let's move on.
Make a Castlevania action RPG. Heck, make a CV turn based RPG if you need. A sidescrolling beat'em up in the vein of Knights of the Round. A 3d "sandbox" game where you start in your small Transilvanian village and keep unlocking new areas a la Assassin's Creed/Ocarina of Time, with real time traversal on horses and carts, a Van Helsing sidekick building you anti-monster gear as you progress through the game, a diversity of locations and enemies leading to the final confrontation in Dracula's Castle (that has been looming over your village since the first minute of gaming, thanks).
I'd be fine with either outcome, to be honest.
The thing that has me the LEAST excited at the moment is the eventual announcement of a 2D sidescroller that is just like SotN except magic this time buffs your weapon this way and not that. Oh and everything else is the same. It's been like this for 13 years now.