Now don't take that literally. What they mean by that is they feel it's a damn safe bet that it'll be a while before anyone unlocks the 25th (and over) character. The good news is they confirm that there is in fact more than 24 playable characters.
This post is orignally from the IGN boards..
Jeff,
Concerning "Mortal Kombat: Deception", here are the answers to some questions in which you e-mailed to me.
1. What are the names 'Fujin' and 'Stryker' in the clouds for in the main menu?
Answer: As far as I know, they are just there for fun, and to give a hint of things to come for future games. It's basically nothing more than an inside joke.
2. Once you beat Konquest mode and receive Raiden and Liu Kang, are there more missions and things to unlock?
Answer: Yes. As time moves on, and you figure out more things, more missions tend to appear. Konquest is huge, and will take a long time to completely find everything that is hidden. As I already told you a while back, every character is playable in Puzzle and can be unlocked. Try looking for them. *wink*
3. Are there more than 24 playable characters. MEANING, since everyone online these days doesn't understand the word 'playable', I mean are there more characters that you can play as in Arcade mode and Online mode that aren't included in the main 24? Sorry if that sounds confusing.
Answer: There are more than 24 playable characters. Try Konquest. If you and anyone of your friends have found them by now, I will give you money. It will be awhile, I'm sure, before you figure it out. From what I know, Midway made sure to hide them really well. It might be a good month or so before you hear one of your friends go "I found the first clue!!"
4. If there are any hidden characters, do you have any idea whom they might be? And are they Raiden and Liu Kang? And is the boss playable?
Answer: They are not Raiden and Liu Kang. The real hidden characters are some characters from Deadly Alliance. The boss, last I heard, wasn't going to be playable.
5. If anything you've told me before is true, could they have taken the secret characters out at the last minute if they are not in there?
Answer: Yes, they could have, but the last I know, they were 100% sure that they were going to include the hidden characters in the final build of the game.
(credit - some guy named Jeff from the IGN board who's been asking midway questions and somehow getting answers)