How likely is it to get full custody of my grandson?

I have had temporary custody since December 2013 but have had him in my care for much longer and on and off his whole life. Both parents are drug abusers and smoke weed. The most recent positive drug test for the mom was in July. She had higher results in July than she did in June. She received a 45 day sentence and only served 5. The dad was sentenced also for not showing up for color code test. The mom is pregnant and due on December 16, which means she was using while pregnant. She has not had any counseling. She also is married to a felon that has never had a job. They live in a 2 bedroom townhouse with her mother in law, her, her husband, 11 year old autistic stepson who was the only one home when his mother OD'ed, and soon to be newborn baby girl. I have a voice conversation with her talking about how she bought and took xanabar in July (while pregnant) because she can since she has a script for klonipin. My grandson has come so far. He makes A's and B's, is involved with church, we feed the homeless and he plays sports. Both parents are on supervised visits, which are supervised by me. I’m scared to death of what may be ahead!