From what I've heard, yes she is going to be in the chrissie special, but it's going to be either a flashback or a past version of herself, seen by the Doctor. The new series is going to start next year with Matt Smith, we've got the waters of mars coming soon though! And the crissie special (the end of time)
Yes she comes in one of the episodes in season 4 but after 2 or 3 episodes after she is there the hand of the doctor that fell off while he was fighting an alien (but he grew a new one) Donna (who is a human) touched the hand and it turned into another doctor but he is a human so The Doctor takes Rose Tyler back to the other parallel world (and since the other doctor is human) he would grow old and die so they got to live together in the other Parallel world.
