E3 will indeed play host to a new Castlevania game announcement, as hoped and dreamed for many months.
A rumor originating from German site n1ntendo (via) would have us believe the game — named Castlevania: Mirror of Fate — is a 3DS exclusive with Lords of Shadow producer David Cox and director Enric Alvarez involved. The information supposedly originates from Konami’s leaked schedule for the expo.
Cox has been a tease about a new game in the past, though a Twitter response leaves the door open for speculation on this one: “..misinformed. I would also say the truth is ALWAYS better than fiction!”