The French need a victory to finish the tournament with style and confirm their excellent performance against Italy. Their first half in Rome especially was the best of the tournament, the game was fluid, the basics were done well, and the half-back combination worked perfectly, preventing the Italians from playing for almost 60 minutes.
This is very reassuring for the French side even if they failed with their two defeats to England and Ireland. They made mistakes and went through hell after their setback in Dublin not only because of the coach's hard comments but also because they had huge regrets. They cannot experience that again against Wales because this is their last match and it takes place at the Stade de France.
On the other hand I am not that surprised to see England and Ireland in the Grand Slam final. The English were favourites, they have not won for three years and were simply more motivated than the French. The Irish meanwhile were the outsiders but they have clearly shown their potential throughout the competition, also becoming great contenders for the World Cup.
As far as France are concerned they will need the summer tour to see what they are really capable of, and it is only in September, after their two friendlies with England, that we will know whether they have what it takes to be strong competitors in Australia.