Historically, it will most likely fall below 200k by mid-January. This prediction does have a number of things going in it's favor though.
1. PS3 sales after the holiday should be higher than past years due to it's new price point.
2. I honestly don't think I can ever remember a non-holiday quarter that is a jammed-packed as Q1 2010. There are a TON of big games coming out early next year including:
-Bayonetta (America) [01/05]
-Bayonetta (Europe) [01/08]
-Army of Two: The 40th Day (Europe) [01/08]
-Army of Two: The 40th Day (America) [01/12]
-Dark Void (America) [01/12]
-Dark Void (Europe) [01/15]
-M.A.G. (America) [01/26]
-Ar Tonelico III (Japan) [01/28]
-Last Rebellion (Japan) [01/28]
-Resonance of Fate (Japan) [01/28]
-Star Ocean: The Last Hope International (America/Japan) [02/04]
-BioShock 2 (America/Europe) [02/09]
-Dante's Inferno (America) [02/09]
-Dante's Inferno (Europe) [02/12]
-Lost Planet 2 (America) [02/23]
-Battlefield: Bad Company 2 (America) [03/02]
-Battlefield: Bad Company 2 (Europe) [03/05]
-Super Street Fighter IV (America/Europe/Japan) [03/23]
-Dead Rising 2
-EyePet (America)
-Final Fantasy XIII (America/Europe)
-God of War III
-Gran Turismo 5
-Heavy Rain
-Lost Planet 2 (Europe/Japan)
-Mafia II
-Max Payne 3
-Quantum Theory
-Resident Evil 5: Alternate Edition
-Resonance of Fate (America/Europe)
-Trinity: Souls of Zill O'll (Japan)
-White Knight Chronicles (America/Europe)
-Yakuza 4 (Japan)
3. Sony has their Motion Controllers releasing in March. If marketed correctly, it could hold PS3 sales above 200k well into June.
So mid-January at the earliest and June at the latest is when this prediction will most likely fail. If I were to wager, I would bet on the week after the release of BioShock 2 in mid-February will be the first week that PS3 falls under 200k.