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?
Looking at the December 2008 FIFA ranking, the order of the three teams tied for 11th place is France, Czech Republic, Portugal. However, looking at the actual values (confirmed by FIFA), the order should be Czech Republic (1007.4), Portugal (1007.07), France (1006.87). That's the order I use for seeding. So the first question is: which country gets more points (24) for the December 2008 ranking?
If France gets the 24 points, Portugal needs 5 qualified teams between it and France in the November 2009 FIFA Ranking. With only 4 teams, Portugal and France will be tied and I don't know the official tie-breaking criteria. France has a better World Cup performance (23.3) than Portugal (22.3).
If Portugal gets the 24 points, it will only need 3 teams qualified between it and France in the November 2009 FIFA Ranking. With only 2 teams, they will be tied.
In order to maximize its chances, Portugal needs to get Ukraine (highest ranked among the unseeded teams) in the play-off and win both matches, with France getting two points against Slovenia (lowest ranked) and qualifying on away goals.
More on this on Monday.