How the Nazis - and particularly Hitler - assessed France has been examined recently by historian Jean-Paul Cointet, so I'll use his analysis to try to answer that interesting question. In a nutshell, Hitler had a unwavering low opinion of France, that he expressed explicitly from Mein Kampf to his latest writings. Hitler's criticism was three-pronged:
France was the "eternal enemy of the German people", and had been trying to dismantle Germany for centuries. And, of course, France had "stolen" Alsace-Lorraine.
French politics were directed by capitalists, themselves controlled by Jews. French antisemites agreed that France was enjuivée.
France was racially inferior, barely Aryan, and contaminated due to the "misgeneation" caused by its colonial empire. In the 1920s, this had been exploited by German nationalists during the "Black Horror on the Rhine" campaign or in cartoons about the "negroization" (vernegerung) of France (as shown for instance on the back cover of the satirical magazine Kladderadatsch of 14-17 April 1932, which shows the "last non-Black French people in 100 years", reduced to zoo animals). From Hitler's Mein Kampf:
Provided that the mixture of races and the resulting miscegenation of races continue at the same rate, it may be foreseen that in three centuries the faint traces of Aryan blood which still remain in France will have disappeared. There will be, stretching from the Rhine to the Congo, a great State populated by mulattoes, by beings belonging to that inferior and indefinable race which is formed as a result of continuous miscegenation.
However, Hitler was not particularly obsessed with France. The political plan that he exposed in the successive versions of Mein Kampf required defeating France, though what was to happen to defeated France was left unexplored. Hitler treated France with contempt: its existence was merely an obstacle to German expansionism. After the swift French defeat of May-June 1940, Hitler did a brief and symbolic victory tour of Paris. The German occupation that followed handled France not as a country, but as a place to be used for military operations and whose resources could be plundered at will and transferred to Germany. Several Northern and Eastern departments, considered to have "Germanic" populations, were put under direct German control and scheduled for annexion. The rest of the country still relied on French (technical) administration. The Nazis occupied the top half and the Western coasts of France, areas that were more industrialized and/or that had prosperous agriculture, and they left the Vichy government have "sovereignty" in the less opulent "Free Zone" in the bottom half.
Germans had no interest in managing French populations, who were neither German-like enough to be somehow turned into actual Germans, nor "subhuman" enough to be simply exterminated like Jews, Slavs, and Roma. The Nazis killed French people who resisted, as well as hostages. With Vichy assistance, they deported about 80,000 Jews, 25% of the Jewish population in mainland France. They did not try to have Vichy exterminate the Jews in North Africa, or the Roma and mental patients in the mainland (who suffered greatly, but the two latter groups were only targeted for extermination in the annexed departments under direct German control).
To put it simply: the Germans did not care about France, except in terms of resources: food, raw materials, manufactured products, artworks, police assistance, forced labour, and of course military facilities, with parts of France turned into coastal defenses, fortifications, and military bases (built by French workers). Goering told an assembly of commanders in occupied territories on 6 August 1942 (cited during the Nuremberg trials):
As far as France is concerned, I would say that we are far from making the most of it. We can get much more out of France if we manage to make the farmers work better. Secondly, in this France, the population is stuffing itself so much that it is a real scandal [...]. But it's not just a question of supplies. I have often said that I consider all the France we have occupied as conquered territory [...]. However, I intend to plunder, and to plunder widely.
Germanization was never part of the process, and the Nazis did not spend resources to turn the racially dubious French into bonafide Aryans. Propaganda was widely used to control public opinion, but racist ideologies, by definition, do not consider that education, let alone language, can change racial identity.
The question of what would have happened if the Germans had won the war belongs to counterfactual history and it can only be speculated about. For Cointet, the Nazi postwar plan was centered on a Great Reich consisting in Germany, Austria, Bohemia, Moravia, parts of Hungary and Romania, Denmark, Belgium, the Netherlands, and the French departments annexed in 1940 (Nord, Pas-de-Calais, Alsace-Lorraine). Scandinavia would be associated to the Reich, as would be a "reeducated" Great Britain. Slavic territories would be colonized and their populations massacred. France, a "deliquescent" nation prone to "fits of nerves" (as wrote Hitler in 1945) would be largely dismembered. Its populations were not to be exterminated, but they were certainly not going to become German and culturally Germanized.
Since France still existed in the periphery of the Great Reich, it would be under heavy German control, perhaps not as a settler colony (unless the Germans were willing to exterminate the French), but at least as an exploitation colony, with its people and resources managed by German operators for the benefit of the Reich. Such an exploitation system would require a layer of German-compliant, German-trained French workers and low-level managers, who would be fluent in German. This is how it worked for the native populations in the African and Asian colonies of the French and British empires: one did not need to teach the colonist's language to all the natives to rule them. However, French and British colonial authorities still had to pay lip service to whatever version of the civilizing mission was meant to be the moral compass of colonisation, so they ended up giving proper education to chosen colonized subjects. Nazis could be hardly expected to do that.
So: would French people in a Nazi postwar speak German in 2022? Possibly a few collaborators kept on a tight leash, as well as some French people considered Aryan enough. For the rest, the Germans would not care about what language the regular French spoke provided that they meet production quotas without complaining. Would the Germans try to improve productivity by forcing all the French to learn German? This is a possibility, but it would have been dangerous: in European colonies, more than a few educated natives went on to lead decolonization movements, and were able to "weaponize" colonial knowledge and colonial language against their masters. But again, this is counterfactual history.
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