In the modern day, it feels to me like "Whiteness" is expanding to include African-Americans. The strongest dividing line again seems to be between established American ethnicities and recent immigrants, and African-Americans clearly belong to the former, in a way that Salvadorans or Pakistanis may not.
Lmao. Summer of the 2020 completely proves this false.
It's true if you think of "whiteness" as "the American cultural mainstream", and really has been long before BLM became a thing.
Asians will not "become white" over time because there is no evidence of this process ever having happened in this country's history. Those that intermarry with whites may have white descendants, but only if those descendants are sufficiently white-looking that they lack obvious Asian ancestry.
Asians have never been in the USA in the past at the numbers we are now so there has been no opportunity for that mixing to have occurred. Pointing to the past does not dictate the future, we have no idea if race will even remain a relevant construct in the future and even if it remains perhaps in a drastically different form than today