All others are equally (not very) likely, in my mind, except Le Pen-Bayrou. In order of decreasing likelihood:
Bayrou vs. Royal. Bayrou wins with the right. Royal vs. Le Pen. Royal wins 60-40. Sarkozy vs. Le Pen. Sarkozy wins with low participation Sarkozy vs. Bayrou - Bayrou wins with the left.
Bayrou vs. Le Pen. Nah. In the long run, we're all dead. John Maynard Keynes
did i miss something ?