So theoretically, if bitmain and all their miners they run shut down, 1-2 days before difficulty change, would enough hashing power come off the network to actually drop difficulty, i would think if that was possible they would be doing that to lock in another two weeks of higher profitability.
and if they think their gov is shutting them down they will mine and dump as much as they can until the shut down.
as for canaan.io
they mention the 20th
but if their gov forbid btc to cash trading they may not sell from china and ship to usa which is why I ordered 1 from the usa distributor