If, having seen how effective the panzers were in Poland, the French react accordingly, they could cause genuine harm to the Nazis.
For instance, having seen the performence, the French decide to change their agenda. While unable to dramatically expand the production of tanks, they do have a substantial number already available. Every corps in the French army is ordered to concentrate their tanks into a single brigade unit, which will have about 6-7 months of training together prior to the German invasion.
Note, I am uncertain as the breakdown of tanks and their number in 1939 France, so this may be too few or too many.
In the actual invasion Germany saw half of it's tanks either destroyed or knocked out due to damage, wear and tear from use, or gasoline shortages, so the panzers were not completely invincible. In fact, the German officers nightmare was a successful breakthrough, followed by an allied counterstrike which isolated the panzers from the following infantry. This is why the small and short-lived counter attack by De Gaulle in the south and the British 1st tank brigade in the north caused such concern.
In this case, two or three French armored brigades are in the path of the German assault, enjoying their intrinsic advantages(armor and such) as well as the defender's advantage. The Germans are held back another week, losing about 10% of their panzers in the process. The campaign otherwise proceeds as in reality, except that the French have more time to plan and bring forward reservists and possibly units in the Maginot line. More importantly, other armored brigades exist and are used to provide a crude armored corps to De Gaulle, and the nearly 100 fighters purchased in the US and on the carrier Bearn also make it to France. The counter attack, now stronger and with some air support, links up with the BEF and other units up north!
The Germans smash forward with their infantry(the bulk) and manage to restore contact, but this effort, the costs thereof, and the need to regroup and resupply is costly. In effect, Germany losses in manpower are already 2-3 times what was lost in reality(120 to 150 thousand), and a shocking report mentions that half of German tanks are destroyed, and that almost all the remainder were broken down, knocked out, or low on fuel at some point.
Ultimately France does fall, with the British taking heavier losses in the campaign and ultimate evacuation of Dunkirk, but the renewed German dependency on infantry means the BEF's escape is never in such great doubt. In addition, the fall of France is further delayed by the fact that French confidence never dropped as low, not to mention the remaining tanks still standing together.
Perhaps some heroic counter attack or final stand by a French tank unit?
All told, France falls about September of 1940.
------------------------------------------------------------------------
POSSIBLE RESULTS:
England: Much more confident, as they have all construction through September 1940 for the military, and for defenses. No Sea Lion possible until spring. British can act with greater confidence elsewhere.
Do they send sufficient forces to O'Conner to take Italian North Africa or does an Africa Korps arrive early to salvage something?
Capture of French colonies, such as Dakar, which would provide Free France with an excellant base and several cruisers, plus an unfinished battleship. In reality the attack here came so close to success that any new strength would guarantee a victory.
Germany: Higher losses, less arrogance, and a wonderful excuse to hasten production of new and better tanks. Hmm, they might actually be more dangerous soon. Does Hitler act in the Med, or does he still focus on the East?
France: Still conquered, but put up a better show. Does this mean a larger Free France, perhaps entering 1941 with 4-6 infantry brigades, several colonies, and a navy up to several cruisers? Does the government withdraw to North Africa, helping crush Italian North Africa and battling for Corsica?