You won't get killed.
Miles for a flight taken on 31st of Dec 2019 will count towards 2019, no matter how late they appear in the account.
A potential delay does not matter either as long as you take the delayed flight.
In case of involuntary rebooking to another flight, you can still claim miles according to your original booking.
Last edited by andywaw; Oct 22, 2019 at 3:37 am