All of those are fine, depending on when Doni actually is leaving for Brazil. :P When present progressive is used, to me it implies that the action will happen fairly soon..because it is the present tense. However, in casual conversation, present progressive is often used even if the action will happen several months from now.
Although it's somewhat a matter of preference, for anything over a year I would use future progressive. "Doni will be leaving for Brazil next year."