Would be nice to think the above but not one shred of evidence to back it up. Lots of evidence that Nazi indoctrination meant they were not seeing Slavs as people just things or numbers, no evidence that the killing was having any pushback effect. Lots of evidence the younger people were the more indoctrinated they had become. Nazis were not nice people, hand wringing and saying but they would have got better does not cut it with those who lost kin to their practices.
Again, my argument is not that the Nazi leadership would not
want to complete a Generalplan Ost like it was planned during the war, or that Nazi ideology would not demand it. My argument is not that the Nazis were "nice", quite the opposite. They obviously were monsters. What I am questioning is whether it would be realistic to expect the plans to be realized exactly in the way that was envisioned. There are many reasons why many parts of the OTL wartime plans would be unlikely, like limited resources and logistics problems alone. The areas the Third Reich would have conquered would be massive, the populations it would be reigning over huge as well. The fact that a government and state apparatus does not want to accept the constraints of objective reality does not mean that it can escape them through pure evil alone. There
is evidence that the OTL atrocities were taking their toll on the German soldiers and ordinary people in psychological terms, etc. This is shown by the fact, referred to above, that the Nazis had to create "cleaner", in other words more impersonal ways to kill Jews and Slavs (which gas chambers, say, represented) as mass executions and other similar "hands on" measures were mentally too hard on the soldiers.
The plans changed over time, and the OTL plans at the beginning of Barbarossa were different from the plans as they were in 1942, various changes happening in only a few months due to war events. I am quite certain that in a victorious Third Reich, the "general plans for the East" would see many different iterations in 1945-1955, say, as the postwar Nazi leadership would have to amend the plans for a new reality. Changes in leadership, and power struggle between various Nazi bigwigs and factions would also have an effect on this. The question about the role of the Heer in the new reality and the success of the plans to make all armed forces part of the Waffen-SS, etc, would also have an effect. The huge rebuilding effort in the Reich would have an effect. So, in reference to the OP - there would be an attempt to complete a Generalplan Ost, it would just be a different plan from what we know from the OTL.