There’s no way the Nazis are hiding Generalplan Ost and that would make the Holocaust look like a birthday party.
Regarding the
Generalplan Ost: it was a plan. And there were many plans regarding the future of Eastern Europe, ranging from the Generalplan Ost to Rosenberg's plans of setting up independent states in Eastern Europe and boxing Russia in. Hitler himself wasn't always set on direct control : as late as 1940-1941, he talked about the possibility of a "federation of Baltic states" and an "independent Ukraine". And National Socialism proved to be quite fluid and easy to change in some ways in wartime.
In my view, a reason why Hitler pushed for the direct control of the East can be found in the way the occupation was organised. More specifically, the General Government was set up in large part in order to
prevent the imposition of standard German law that would result from a direct annexation to the Reich itself: Hitler wanted Frank not to be "shackled" by the nuisances of legality etc. in order to achieve what he deemed as vital for the German people (this however proved to be a bit ironic, as Frank proved to be thoroughly arbitrary in his administration but presented himself as the staunch defender of the position of the law in the state)
The same reason was largely behind the creation of the Reichskommissariats, as Hitler wanted the lands of Eastern Europe, which were central to his plans and ideas, to be ruled by people loyal to the Party, men of decisive action and political activity (supposedly), rather than brow-beaten administrators trying to minimise the demands of the army and the government, sticking to legal procedures that were "remnants of an older, liberal order" and in general being a pain in the ass for Hitler and his visions.
Also, even between these Party men, there were differences of style and ideas, ranging from Wilhelm Kube to Erich Koch.
Erich Koch was the
Reichskommissar of Ukraine. His idea of government didn't extend much further than systematic looting of the area, surveillance and repression, while he demonstrated an extremely racist behaviour - largely politically motivated (casually calling the Ukrainians as "niggers"), despite the fact that his administration came to rely quite heavily on the locals. All these brought him to conflict with many, such as Rosenberg, Berger (Himmler's man in Ukraine) and more. Despite all these however, he managed to retain his position, but still, his rulesl was dependent almost solely on brutality and force.
Wilhelm Kube was the
Generalkommissar of White Ruthenia (Belarus), an
Altkämpfer, convicted of embezzlement, demoted in the Party and sent to the area partly as punishment. Unlike Koch however, whom he had many shared qualities with, he managed to maintain an element of political pragmatism in his otherwise similarly brutal administration. While his police brutally massacred Jews en masse and few other places in Europe were as much as or more devastated than Belarus after the war, Kube viewed himself as a patron of local culture and was to an extent aware of the limitations imposed by his limited manpower and therefore, more willing to turn the locals into an anti-Russian force. Thus, he did things like creating a personal guard consisting of Belorussians, allowing the creation of local political and welfare organisations and making the teaching of Belorussian compulsory at local schools, while forbidding Polish and Russian.
Therefore, despite it being more like "the worst case" and "the slightly less bad alternative", there were variations in administration in the occupied Eastern territories. In my view, if Germany won the war there would be massacres dialed up to 11, but in the early 1950s, the imminent economic collapse due to the Eastern territories having been royally screwed and the economy having overheated way too much would force Berlin to halt at least the genocidal part of the plan and turn death to forced labor /slavery.
But this is only one of many possibilities, as much depends on when the Führer dies, the dynamics between the many power centres in Germany like the army, the Party, the SS, the bureaucracy, the business elite etc. By that I mean that we could see almost everything, from Eastern Europe being turned to a gigantic version of Khmer Rouge Cambodia, to an occupied East with Germans being pushed to settle in areas like the Baltic region, Crimea and southern Ukraine and the locals reduced to second-tier citizens, to (in case the Nazis screw things up too much even for their liking and in any case, a rather unlikely, but not impossible, scenario) the creation of puppet states in the East ala Brest Litovsk (but with much more blood and close supervision by Berlin). Because, as mentioned above, National Socialism would most likely ITTL as well prove to be extremely fluid as an ideology and thus many could and would frame it, define it and spin it as they liked in order to get over practical difficulties.
