Oh, so the 3DS is the next "new" Nintendo handheld console? That sounds like a great successor to the DS line. It'll be great for casual games. Man, until I've seen it for myself, it'll be hard to say if it'd be something worth trying out on a Castlevania game. Castlevania certainly doesn't need 3D and any attempts to utilize it might be rather lame and gimmicky like using the Stylus at the end of boss battles in Dawn of Sorrow. It might be novel for some visual effects, but whether it would enrich the game play experience or be an annoying distraction is hard to say. But another thing about the new 3D is that it has higher processing power and better resolution. That might be the reason to make a new Castlevania game for it, with perhaps the 3D stuff added as an after-thought? Of course, they might feel "pressured" to utilize its 3D effects like they were the Stylus in DoS, so it'll probably use it somehow. But will it be an optional gimmick thing that you could disable, or would the game be built around it? Then there's the whole question about how 3D would be used. Would it be like Dracula X Chronicles for general style with certain stuff in the foreground and background? Maybe it could still be sprite based, but with extra layers using sprites or polygons in the foreground and background. Could it be a full 3D game with a behind-the-user perspective like Castlevania 64? I imagine that a slanted overhead view (like Gauntlet) would work best for a fully integrated 3D Castlevania game.
I still might consider buying the DS XL. For me, the whole point of getting it is to enjoy the current DS Castlevanias more. I don't think playing them on the 3DS will make them any more enjoyable. So its then just down to how much $$ I'm willing to spend and when.