First of all, I assume FIFA will use the same seeding formula as in 2006 (see Wikipedia) and both Portugal and France will qualify.
What does Portugal need in order to be seeded?
Read the first part and Dorian's insightful comments.
It's possible for Portugal to be seeded even if it gets only 23 points for the December 2008 ranking. If France gets Slovenia in the play-offs and qualifies on away goals with two draws, with the other three seeded teams (Portugal, Russia and Greece) winning both legs of the play-off, there will be 5 teams between France and Portugal: Russia, Argentina, England, Greece and Croatia.
I will post an update after the draw - if time allows.