Different levels of undesirables
To the Nazi's, the real undesirable racial/cultural groups, as far as I see, were the Jews and gypsys. They would be exterminated utterly--or as utterly as they could. I'd guess the early 1950's, and one part of the holocaust is complete--the extermination of the ones on the "wipe them out" list.
The Slavs were seen as subhuman; the holocaust would be ongoing in the sense of first reducing their numbers to a "desirable" level, and then treating them worse than any ante-bellum southern aristocrat treated his slaves.
The third part have to be a permanent part of the system, as defectives and homosexuals will keep showing up, and need to be wiped out. I suspect that defectives born later would be euthanized cleanly, like in one of Turtledove's books at a "Reich Mercy Center." (Not the Race series, the book that was a parallel to the collapse of the Soviet Union--can't remember the name.)
Of course, for generations, there would be the occasional "Jew hunt," if evidence was found or manufactured that someone's enemy has Jewish blood...
Likewise, homosexuality would be something to accuse someone of if you wanted them dead or out of power.
In this sense, the Holocaust continues indefinitely, even without a new target list. Having homosexuals on the death list might be enough to make creating a new "primary target" unnecessary, as they can be used as scapegoats whenever something goes very bad--traitors in high places, etc. (That also gives a chance to purge the Gestapo department that "missed the obvious perversions," or promote them when the "discover that X is starting to turn traitor...)