>>513957411 (OP)Not a scientist, but basic science disproves this.
Like blue eyes, blonde hair is a recessive allele, meaning it can be carried even when masked by the dominant phenotype and therefore is not exposed to the same kind of selection pressure e.g. you can marry a brunette and have blonde kids as long as her mother was blonde (as long as you have one blonde allele that may or may not be presented in your phenotype).
Alleles can only die out when the gene pool gets much smaller, which is impossible when relaxed immigration and intercourse laws means practically everyone is travelling and having kids with each other.
Again, not a scientist, but logically it would be preferable to spread those recessive genes out so everyone has them, no? That way two Bbs like in this image can make a bb (blonde) baby. And given the fact that blonde hair tends to be an attractive trait to most people, I don't think it will die out to being selected against. It would be different in the case of some harmful recessive genes like cystic fibrosis or sickle-cell anemia.
Low TFR will kill white genes more than racemixing will.
Also this is a hoax.
https://en.wikipedia.org/wiki/Disappearing_blonde_gene