When was the last time Republican presidential or Congressional candidates talked openly about how blacks have fared under the Democrats? Not even Reagan had the guts to talk about this. Directly, not in a "low taxes benefits all" or "enterprise zones" type of talk.
If Trump gets even a quarter of the black vote, Hillary is toast. And note that Trump is not pandering to blacks or being condescending and accepting their premise that everything is whitey's fault and he'll make it better.
You are correct, whenever the day comes that the democratic hold of the Blacks breaks wide open, it will be the age of a new political era in America.
The critics of Trump's appeal for a chance from the ghetto dwellers essentially say it is a losing appeal because he is not pandering to their :oppression framework" (my choice of phrase, not a quote).
Of course the grievance industry is opposed to Trump, as is the uniparty approach, wich aims to keep the populace down, to benefit the controlling class.
If noting else, this will get them talking amongst themselve. Seriously, what do they have to lose? Roll them bones.