Here is my personal opinion on who the mysterious African Amercian Character..i am going to say that:
J Augest Richards is Elijah Bradley (AKA Patriot)
Here are my 4 Main Reasons for this:
1.He looks very similar to Patriot
2. Some of Patriot's abilties are demonstrate in this trailer ( The Super-Speed and the Super-Strength)
3. In the trailer they make a reference to his S.H.I.E.L.D., which i think is hinting at Elijah Bradley later becoming Patriot
4. In one shot of the trailer...he is clearly using some sort of drug..could it be the Mutant Growth Hormone with a different name..it is centernaly possible..
So who do you guys think is the person in the trailer..i think it's Patroit but i could be wrong..but it is not Luke Cage..