AFC have announced the draw for the 4th round will also be based on the FIFA rankings.
The last match day of round 3 takes place on February 29, while the first match day of round 4 is scheduled for June 3.
I think the draw will take place in March, using the March FIFA ranking that will be released on March 14.
4 years ago, the 4 lowest seeded teams of the 10 qualified for the 4th round were placed in a single pot.
Here's the March 2012 FIFA ranking, counting scheduled games as defeats (only teams still alive):
Pot 1: Australia, Japan
Pot 2: Korea Republic, Iran
Pot 3: Uzbekistan, Iraq
Pot 4: Jordan, Bahrain, Saudi Arabia, Kuwait