When I visited AF website (http://www.airfrance.com), I was surprised -- they now operates only 5 Concordes!!! Everyone know, that AF bought 7 Concordes. Is AF retired two? Where these Concordes disapeared?
How about if the US decide to be petty and ban England and France from flying these beautiful airliners into the US. I reckon there wouldn't be much of a life left for them then. Perhaps just charters to the Carib'.
As far as I know, the other two Concordes are used for VIP Round-the-World-flights or special promotions (remember the Pepsi-Concorde?).
It's also possible that they use one for spare parts, as DeltaAir suggested.
All in all, AF's Concordes are used much less frequently than BA's.