I don't think Macron winning is a done deal to be honest, but if she wins, I think it will spell the beginning of the end for the EU.
I was intrigued by this possibility a few days ago, and actually, it transpires that the French President isn't anywhere near as powerful as it seems. They are mostly ceremonial in nature, but because there are elections to the National Assembly shortly afterwards, it usually meant that the party winning the Presidency would win in the National Assembly as well. In this case, there's no chance of the NF winning there, so she could potentially be a lame duck president, similar to how Lech Kaczyński was under PO.