Does anyone know when the AO MD cut off week is?
Yes, the main draw is determined based on the rankings as at Monday 05 December (6 weeks prior to the tournament start, as usual). In practice though, because this coming week is the last week of Challengers for the year, it's basically the rankings as at next Monday.
Ducks will go from 104 to 102 at the start of the week due to Nishioka and Cervantes falling behind him. Nishioka is playing in Astana, but has to win that tournament to go past James again. The only real danger is Jared Donaldson in Columbus, with Stakhovsky and Chiudinelli also chances if they win their respective events.
As a comparison, Ebden just missed out by one with a ranking of 105 for this year's MD.