I doubt any candidate will exit the euro, except the extreme right.
Socialists will win unfortunately.
My prediction is that "extreme right" candidate Marine Le Pen will make it to the second round but then the theatrical "Fascist" thread will make her opponent (whoever it'll be) win.
I even doubt either Hollande or Sarkozy will make it to the second round. There's a great political despair in the French population.
But I agree the next President won't exit the euro and that's their tragedy. Once Greece and Portugal had exited it, euro'll be far too high for the French and that will be a disaster.
Actually the French don't just need to exit the Euro but also the EU. Every decision they have to make goes against the Maastricht Treaty and the EU general rules. Concerning their public services, their agriculture, their industry, their foreign policy, their immigration policy, etc. But no candidate suggests that, except very unknown ones.
That's the Gaullist in me speaking.