By 'mainstream', I mean that Vtubers like in Japan would be on the morning talk shows, be featured in advertisements on TV, have shows about V-Tubers on TV (there is a light novel with an anime adaptation called VTuber Legend: How I Went Viral After Forgetting to Turn Off My Stream), collaborations with V-Tubers and sports teams are a common occurrence, and while we have had some of these things in the West, it's not as pervasive as it is in Japan.
In my opinion with Western media being continually ass, it's only a matter of time.
It actually is, but only to a certain subset of other black people who's entire personality is "black culture".
Most black entertainers have a hugely disproportionate black audience. Only a handful of real stars attract a broad spectrum audience, but hundreds of C-listers coast along almost entirely on in-group bias, "how do you do fellow blacks" jokes, and a willingness to take potshots at black superiority over other ethnicities.
Same is true for the handful of black vtubers, except they're barely making it because being a vtuber simp isn't very congruous with the rest of "black culture"