After a space of 100,000 or even 10,000 years, our descendants would be so far apart from us that they'd feel like a different species altogether.

It doesn't really matter. However different they will be from us, they will still be the closest thing resembling us genetically and phenotypically compared to other races and species. Maybe you don't care about your descendants surviving long-term, but I sure do. Of course, assuming we will win, eugenics and human genetic modification can also do its part in "fossilizing" traits common in whites, while making beneficial traits in whites more prominent and dysgenic traits less prominent. But no matter how different our descendants will be from us in hundreds of thousands of years from us, this will be such a gradual evolutionary process that we won't even notice it. Whites from 10 000 years ago were pretty much the same as us genetically and phenotypically, so assuming we will manage to stop dysgenics by implementing eugenics and human genetic modification, whites from 10 000 years in the future will still be very similar to us, definitely similar enough to the point that they would be biologically classified as white by today's standards.