We don't know if the Castlevania game rumored for 3DS will be 2D or 3D, but I'm sure something is coming. IGA's had a devkit for a while, he's stated he has ideas for the series, there were rumors reported back in December that he was involved with 3D modeling artists, and there was a report a few months ago that MercurySteam made a prototype Castlevania running on 3DS, using the gyrosensor.
I think there's no way Konami would ignore announcing something, given the buildup for a title to be on 3DS. The fact it's the 25th anniversary of the series makes it icing to capitalize on such an occasion. Mario, Zelda, Sonic, Final Fantasy, Dragon Quest, Contra, and even Castlevania have indulged into anniversary events in the past, or are currently. I just hope that if we get a game (it seems likely IMO) that it'll be a better anniversary-esqe title than Portrait of Ruin.