Would definitly love to see new content for old planets, mostly for those who are part of instances (returning in darvannis during kotfe was really enjoyable). But i guess making them other areas like black hole, or sector x would prevent the lvl sync problem and the resulting loading time. Though, i don't know why everybody is excited for datooine but, in my memory, it was trully one of the most boring planet of kotor.
However, i don't think it's a good idea to have only revisiting content for a new expansion, new planets are also needed.