I believe that yes, Marion Barry will be remembered not for his incredible contribution to the civil rights movement, but for his mistakes. This is the way of the world and especially the American way. The day that he passed away, almost every single headline that I read mentioned his drug use and not who the man was, or what he did with his life. It is a true shame that his contribution to the civil rights movement will be all but forgotten because of sensationalist media.
It is unfair to judge someone for something they did years in the past when they have made a good amount of contributions to society. It is also unfair to judge the situation not knowing the details surrounding the events Barry found him self in. Though it involves illicit drugs, I do not believe he should be remembered for those events alone.
No, he will not be known for anymore than that in a few more years time. Nothing he did, has done, or will do, will ever overshadow the crack cocaine scandal. No matter how close a person is geographically located to his area, they will only remember his drug use.
Unfortunately I do not think Marion Barry will be remembered for much more than his drug use. Drug use has a way of labeling a person and when you have someone who is addicted to crack cocaine that often becomes their whole life. When that is the case they don't leave much of a useful track record.