words and phrases change over time yes, but generally the majority goes along with the most commonly meant/implied meaning, so at this time frame it can mean an ignorant person who's black, but in 20 years mean a greeting expression to anyone.
The word has had many different meanings since the most infamous times in society and has changed yes; but that does not mean so many years later it is something completely different. It has modified according to the way people by majority use it, but it still is not a term that's neccesarily compliment all the way, it's still a derogatory term. Some people may associate themselves with it to label themselves as part of a subculture or call someone with African descent an offensive name.
Just like the word gay and it's double definition; it used to mean happy years ago but it is now more known to identify a sexuality. It changed with the majority use by society.
Some people call themselves 'black' when they are not of African descent or call a person of non-African descent 'black' because of the way they appear, talk,etc.
In short words always change meaning, I'll give you that, but leniency is given over time and not just immediately(referring to the dual nature of the word in this time frame).
So yes and no basically.