The section about this says:
1. IMPORTANT - APPLY FOR YOUR CARTE DE SEJOUR NOW!
One thing I can tell you is that as we thought, it WILL become compulsory to hold a Carte de Séjour after Brexit, either from the end of the transition period if there is a deal, or (in theory at least) by 30 March 2019 in the case of no deal.
Those who currently hold cards will have to exchange them, but will find themselves in a stronger position and will be able to take advantage of a facilitated procedure for this exchange.
So the advice is clear. If you’re waiting to see, please start the process now.
Make sure you ask for a récipissé once you’ve put in your dossier too, if your prefecture issues them to EU citizens (not all do). We’re working with both the ministry and the Embassy trying to persuade them to put into action a joint information campaign to give this advice an official stamp, but time is short. Please don’t wait for that to come out before you act.