QoS delisted at (2.245*OW_actual), for Spectre that would be 158.08
Skyfall delisted at (2.711*OW_actual), for spectre that would be 190.91
Difference is those both had thanksgiving during the 2nd week, Spectre has it in its third week. The weekend after thanksgiving it strong, however the weekend that follows that usually hits with a pretty harsh drop.
QoS had a 30% drop the wkend after thanksg, and a 64% drop for its 4th wkend.
Skyfall had a 14% drop the wkend after thanksg, and a 53% drop for its 4th wkend.
Spectre's 4th weekend will be the weekend after thanksgiving so the harsher drop won't hit until its 5th weekend.
An early-early guess based on Skyfall, QoS and Thor 2:
Week 1: 85-90
Week 2: ~45
Week 3: ~25
Wkend 4: ~10
Delist approx 165-170 which is about 2.34-2.41*OW_actual, closer to QoS than Skyfall.
Worldwide it looks to me like 850m is the floor even with just modest growth in China. It has an outside shot at a billion but I'm thinking low-900's is where it'll land.