That's why the OED thing is a bit annoying but at the same time it's understandable. Black people only make up 13% of the population so I don't think OED is ever going to put something in there from the black community unless white people start using it.
But I think this is an aspect of the relationship between culture and subculture at large. I think it's going to be difficult, if not impossible, for any concept to be considered desirable and attractive while arguing that its use and adoption should be limited, especially to the subculture where it originated. This is where, perhaps, twerking and Native American headdresses might differ, for (as far as I can understand it) the discourse surrounding the latter is as much about the important limitations and austerity concerning the use of the headdress (even in Native American culture), whereas the former is a championing of its acceptance as a form of expression.
Granted, its wide remit and focus on historical content may not make it the most relevant authority, but with the OED specifically it is important to remember that it caters to English-language speakers across the world. I know this forum has a particularly American focus, but that includes, for example, the proportion of English speakers in India, for example, as well as those in UK and those in many other countries who use English as a second language. Irrespective of the ethnicity of those speakers, a concept is going to become more relevant to use the more people use it. Based on sheer volume alone, that's more likely to happen when white people start using that word too.
Although I have my own difficulties with the concept of gay identity itself, as a gay man I see an analogue with how anal sex is starting to transfer from within of the (male) gay community and into the wider community. As much as this provides a validation of gay culture, it also acts as a risk by threatening to extinguish yet another aspect of gay identity that distinguishes it from the mainstream. And the gay community (like many other subcultures before it) is going to struggle with responding to it - if lots of straight people start having gay sex, then what's so gay about it?
Edit: So, with regards to acts like twerking and the tropes and meaning that accompany rap, I do believe that in order for those acts to be truly recognised, acknowledged and admired, at one point they will invariably have to leave the black culture where they originated and take their own position in the mainstream, white culture, one which will then maintain no innate connection to the black culture that spawned them. And, surely, it will be better if black artists gain the acknowledgement they deserve for helping to build that culture in the process. But I dare say that if it weren't Miley Cyrus twerking now, it would be some other white artist in 10, 20, or 30 years time. To me, as I have argued previously, what is most pejorative about the discourse is how these acts and identities are often still denigrated in the subculture where they originated after they have been appropriated into the mainstream, and that I think is something which is going to be most effective to change.
