I don't think they've decided that they are going to keep secret characters yet. You've probably heard the interview but this one girl asked him if they would keep some character roster secret and he said I don't know because they characters are the biggest selling point to the game and even said because that interview revolved alot around characters.
I see them announcing characters everywhere they go.
They announced at e3, evo, and comic con. If they are attending a convention they have a plan to make themselves noticed and not just "play the game" but look what we just added. And again they all know that characters are the selling point so if they go somewhere they know they have to deliver.
I would love a couple of characters that are not known. But I'm just using these as examples, if they did have Crash and Spyro they would have to tell people publically because based on these forums people would flip out and pre-order that game immediately. I think could characters that are left secret would be more middle tier characters that are known but not as popular. I would put characters like, Tomba, and the Journey Traveler. If they have enough characters on the roster I would love for a Cloud or Sora to be entirely secret because when that "Sora is now unlocked" I would flip.