no, it's just like saying, "He's the one that's going to take out the trash." The correct way to say it is,"He's the one who's going to take out the trash."
1. I leave tomorrow. 2. I'm leaving tomorrow. 3. I'll leave tomorrow. 4. I'll be leaving tomorrow. 5. I'm going to leave tomorrow.
All are correct. All have basically the same meaning. The differences are just slight differences in the conversational contexts where you would use them. These contexts are so subtle and numerous that it is impossible to explain each