How long?
From my first hand observations, equality of opportunity has been a reality for at least 30 years. Failure to seize that opportunity remains the main problem.
It is a major problem. The inequality of opportunity today is not in hiring or college admissions, but in the inequality of preparation for those opportunities -- because the poor, disproportionately but not all or even mostly black, go to crappy schools, come from broken families, and while many make poor choices, many are also burdened by the poor choices of their parents.
It's not just a mater of bad choices by individuals. It's a culture that makes bad choices easier and good choices more difficult. Where academic achievement is "acting white" and acting like a thug is "keepin' it real." That, not systemic racism, is the problem facing Black Americans today.
I would like to think, had he lived to today, Dr. King would be on the podium opposite Bill Cosby. I'm not confident, but I'd like to think.