The FN was supposed to win the first round with 30%, instead they barely squeaked by Fillon and Mélenchon. Then they were supposed to keep Macron below 60%, instead MLP set herself on fire in the debate.
Keep in mind that the législatives also feature a runoff (not quite the same as the presidential elections though - it's not top 2, but everyone who gets over 12.5% in the first round), so the Republican front should help keep them out of most seats, as they did last time.
The FN has power at the municipal and local level, and at the European level (since unfortunately no one takes those seriously), but not at the national level.
I'm hoping Macron will make the European elections more important to French voters, so that we can finally get rid of those jokers.