Catherine will always be Catherine. She'll just be known publicly by a title. That's it. Princess William, Duchess of Cambridge, Countess of Somewhere.....doesn't matter. Everyone here will still call her Kate or Catherine, the press will call her Princess Kate/Catherine regardless.......so it doesn't really make sense for anyone here to get their feathers ruffled or their dander up over what she'll be called publicly. People will call her whatever they want, no matter what.
Feminism to me is much like PETA. There are many with good intentions, but there are too many who go overboard and make everyone else look bad. Catherine isn't losing anything by marrying William. Everyone gains. Marriage is addition, not subtraction. It doesn't matter what you're called now, or what you'll be called after.