What would have happened?
Depends on whether they can stop the forces moving through Belgium somewhere short of Marseille...
Assuming the defeat was that their failure to make it across the river - as I understand it all but one attempt failied IOTL - kills that part of the plan then presumably there will be a longish delay before the panzers show up somewhere useful. They will have to be fed back through the rather poor Ardenne road system they just tore up getting to Sedan and then there is the issue of where to?
Also how long, a week, a couple of weeks, months? Meanwhile the allies have to stop retreating and do enough damage to the force comming through the low countries that when Guderian and friends show up they can stop that too. Would the panzer force be sent in to a different part of the border - there is after all a reason they keep invading Belgium - or reinforce the earlier attack?
I don't have a detailed enough understanding of the real events, road network etc to know what the realistic chances of the French army staging its victory parade through Berlin on Christmas day...