I believe the "secret" that has to do with Catwoman isn't that there will be a cowl/ears...that detail seems so small and it's basic common sense that she would have cat ears at some point that I don't see why Nolan/WB would want to keep it secret.
Keeping a cowl/ears secret would be like keeping the fact that Joker wears a purple suit secret.
Keeping a cowl/ears secret would be like keeping the fact that Joker wears a purple suit secret.



t:
I was speculating. I never said that was a fact.