This is a very controversial topic. All you have to think about is the controversial decision of the Oakland school board that advocated teaching some of their students in Ebonics (AAVE), because this is what they spoke at home.
As you can imagine, some believe that Ebonics is not a language, but there are other who see it as sufficiently different from English. They state that patterns of Ebonics differ at times substantially from English not only in pronunciation, but also in grammar and vocabulary. And the important point in this discussion is that these differences go beyond what is called slang.
Here is a brief linguistic explanation of the copula:
"The copula system (the organization of the forms of the auxiliary verb "to be") in AAVE is different from other dialects of English. Where other dialects show two forms of the copula: "He is tired out" and "He’s tired out", AAVE has four "He is tired out," "He’s tired out," "He tired out," and "He be tired out." Labov argues that where other dialects contract, Black English Vernacular can delete the copula, (e.g. "He’s tired out" can become "He tired out" in BEV). The "He be tired out" in AAVE implies long and ongoing tiredness."
In light of this, there seems to be shift that Ebonic is its own language. I will link a very informative website on a conference on this topic.