I think this clear strong vote for Royal reduces the risk. It seems to me there's an intent behind it: let's not get caught out like the last time. Let's unite behind a good candidate.

Chevènement (sovereignist ie anti-EU left) has announced his candidature again but said he will desist if there appears to be a risk of a Sarko-Le Pen second round. It doesn't seem likely the Radicaux de Gauche will field a candidate (pity in fact, since their candidate, Christiane Taubira, is a black woman and has plenty to say and says it well). The non-PS left is wallowing around in a mess and currently polling weakly. (Pity again, since the Greens are almost disappearing in this mess).

The remaining query is: will Fabius be tempted to run a rogue candidacy? He got 18% in this primary. He's not considered credible by the hard left. He doesn't appear to have a base there on which to run. If he does, it will be a vanity thing. Would he succeed in splitting the vote? Possibly, but he might get a backlash against him.