Have you read the new Club Penguin Times newspaper yet? If not, you definitely should! Open it and go to the back, then click the "Secrets" section for some major news regarding the future of Card-Jitsu...
As you see, Sensei is hinting us for the next level of Card-Jitsu, which is Card-Jitsu Shadow! Somehow we will get to know Sensei's secret brother, which may be a part of the secret ninja group, the "kunoichi".
By the way, who or what is that figure behind Sensei?
It sounds like the practice of Card-Jitsu Shadow has a long and deep history to it, I can't wait to learn more!