I agree. Trump has already gone on record, numerous times, with his opinion that the AG serves HIM, not the US and that he would not have appointed Sessions if he knew he'd recuse himself and appoint a Special Counsel. He will appoint someone who will serve his interests and hamstring or fire Mueller.
The good news is, it sounds like Mueller is nearing the end game and working on his final report. Trump might listen to his advisers who will say that firing Mueller now will be worse then letting him finish. The problem is, that report goes to the AG and the AG decides what to do with it.
If its damning of Trump, it wont be released. Im not sure if the House can demand it (or release it). I would think so, but I dont know.