I doubt that KOTOR 3 has been planned. SWTOR is the main project now. Also, novels are being released to explain what happened before the events of SWTOR.
Furthermore, even if KOTOR 3 is planned, I doubt that Exile would be a playable character in it. She is dead and would be in the form of a Force Ghost at maximum with whom we may interact during game. Revan can be the main character of that game though, if he is alive.