That looks like the most likely outcome.
It's going to be a balancing act for Macron. The establishment are falling over each other to endorse him, which helps his cause amongst Fillon voters, but it hurts his anti-establishment credibility. I'm unsure if he can convince the left to come out and vote for him.
I think it'll come down to how terrified they are of Le Pen, rather then any policies he presents. (Anecdotally, "I'm scared of Le Pen" seemed to be the motivator for the majority of people I spoke to whilst queuing up for two and a half hours to vote in St Kilda yesterday)