Castlevania will follow the gaming industry, as will all other franchises. I definitely think download is the future, which saddens me a little cause it doesn't really feel the same, but what will be will be...
I don't think IGA will be making Castlevania games in 10 years, he'll eventually wanna do other things.
In 10 years we'll have someone completely new, probably someone who's, like, 18 years old at the moment. There are soooo many talented people who'll grow up and take over some very big positions in the industry.
I wonder what games will look like in 10 years time... we've come to a point where graphics are near photo realism already. There's always room for improvement though, I guess...