The CV series has fallen to it's current state due to two reasons:
1.) Stagnant gameplay and lack of ideas
2.) Failing storyline
Unfortunately, IGA will continue to make games that adhere to these two reasons for the ultimate reason: People still buy them. Game producers equate sales of games as a green light that whatever they are doing, they're doing well and should continue to do until consumer sales wane. I believe, since CV fans have been so starved for a game that eliminates the aforementioned major problems, that we (to quote a recent review) "Dive at any scraps of meat as if it were fine stake", and thusly initial game sales are good.
In order for the series to take a innovative and fresh turn to gameplay and storytelling, IGA and Konami both need a swift kick to the balls in terms of critical reactions to their games and game sales. I do think that, short of Konami all out replacing IGA or a "tragic accident" occurring, we will have to deal with IGA's way of doing things for a while yet. (since I don't see him stepping down anytime soon...especially if he thinks he's doing good by the series)
Due to this, it's up to the fans of Castlevania to send loud and clear messages to IGA that we may not be satisfied with the current trend of his games. However, unless a large coalition of fans goes so far as to physically get up close and personal to IGA to tell him straight to his face what's what, it looks like game sales are the next best possible way to get things across. Unfortunately, it's doubtful that this will happen because we love our series too much to just collectively abandon it in hopes of forcing IGA's hand....because if games like Portrait didn't drive us all away by now, we're not going anywhere despite how much we piss and moan.