>>513585126 (OP)race isn't a thing to begin with and the same genetic drift and environmental differences that caused the current and former batches of various traits will shape future ones
so yes the old categories of race theory will become further and further removed from actual biology but no humanity is not going to all look the same...
unless something kills off everyone but the population of a small self sustaining country that from that point on never leaves it's borders
numbers and distance made the variations to begin with, you think that's suddenly not a thing?
bearing in mind that something like the apocalypses scenario described happened at least twice in every genetic line tested meaning that we got to where we are now in less than 80000 years from a starting group of a single 'race', TWICE, with some tested showing multiple bottlenecks