Oh, please. Don't get me started on this. Except you already did.
Okay, short: Portrait of Ruin has medieval, steampunk-ish guns. They are not your ordinary Desert Eagles and pump-action shotguns. Putting castlevania into future is pretty much like making Hellsing Doom. Just make your own game with own story. That's not a hard thing to create if your brains have any of that *gasp* imagination.
And Castlevania ain't that Castlevania everyone loves if it's in FPS
EDIT: And holy POOP, please fix those sprites!