I got this info from the same Game Developer's Conference about IGA:
Koji Igarashi joined Konami in 1990, starting out as a writer and programmer for the pioneering dating adventure Tokimeki Memorial. He went on to work as associate director on Castlevania: Symphony of the Night, and eventually director of the series, before moving into production duties elsewhere in the company.
See...
We're not downplaying. We are not just fond of speculating when there is no concrete proof of something brewing up.
I just don't think IGA will be back for Castlevania, unless I am proven otherwise.