Will the establishments then turn away from Macron next election, when they can put up more formidable candidates? My American birds-eye view is that Macron is not very popular.
There is no establishment. The classic left party just died while the classic right party still hasn't found anyone popular enough to represent them. Macron isn't very popular during his exercice, but it has been like this for French presidents recently. If nothing changes, Macron may very likely win the next election. Things can change fast though.