Nah, overall if you look at it there won't be a disappearance of the Black community but it will split regionally.
Black folks in the South, Maryland, and a few other places with a critical mass will largely marry and have kids with each other, especially in large metro areas. The mixed Black population will grow as a percentage but I don't think it will get past 1/5 of the total.
In other more 'liberal' areas like the West coast, much of the Midwest outside big cities like Detroit or Chicago and the far northeast, I expect the Black population will have a lot of mixing. The question though about the survival of the Black communities in these areas are how the mixed people identify and who they have kids with. Since mixed Black women are only having kids with Black men 50% of the time and mixed Black men are having kids with Black women only 30% or less of the time, I think a lot of those mixed people won't identify with the Black community overall so you will have aging legacy Black communities where the young people either swirl or emigrate down South.
The US Black population is too big and too segregated to completely mix like Brazil. On the other hand, absent immigration, the Black communities in the UK and Canada (esp. outside Ontario) are on their way to assimilation. Those communities largely never got best reppin' their parents' home countries and never formed a cohesive community. The Caribbean descent will go first and the African descent may hang on for an extra generation or two.
Economically I think there could be a chasm though as a minority of educated and well-off Blacks (like 10-20%) are hanging on the middle class status while the rest are poor.
I actually put numbers behind this in
another thread here