Nov 9, 2018. After 16GP. I'm being scientific, I looked at the schedule.
The killer roadtrip sequence preceding will be the gangplank. The team at that point will have 10pts in 16GP. Unfortunately the schedule from there does not get any easier for the new Head Coach, whoever that may be.
But at that point the org will HAVE to fire McLellan or risk another season. That, already, would be the kills witch point beyond which there is no climbing back.
I can't even imagine a scenario of this team being .500 after Nov 8.