When they were talking w/ Michael McKean in the after-show, he sounded like he believes Chuck is dead.
Can't believe they'd have him survive the fire. Chuck's last words to Jimmy were very powerful & should help kick him along the road to Saul. If he were to somehow survive, the words lose (IMHO) much of their power & provide Jimmy another chance at redemption by caring for his now disfigured mentally unstable brother.
And, dying by himself in the fire makes Jimmy's statement at the beginning of the season that Chuck would die alone & in pain prophetic. (Though not a particularly difficult call.)