Lelouch will go mad, but the night before he'll have said to Karen "If I'm ever to fall I want you to lead for me.".
When Lelouch goes mad, he kills Suzaku, and then kills himself after realising what he did. C.C. will try to save him, but fail. She will continue to live on forever in a secluded mountain range where she will never meet anyone again.
Karen takes back Japan from Britannia. Then half of the world. Britannia surrenders upon the almighty power of Queen Karen the First of Japan. Karen rules the world for a couple more years and everybody thinks she is a great queen. Some scientist create a medicine to give immortality, and she drinks it. She continues to be Queen of the world, forever.