I think you have a couple of factors going on here. I always say that the doom of black culture is assimilation. Its not bad, its not good. Its inevitable. You're not going to have the same soul come out of the middle class suburbs for the most part, that people in rural towns or the old inner-city. Playing instruments isn't cool anymore. Almost no jazz or blues influence. And for hip-hop alone, that true grime experience is a bit different now. Those dudes were influenced by music people and not necessarily just rap people to go along with that grime. Where will that group of music people come from in the next generation? I think that's the difference you can feel with some artists like Kendrick or even Lupe. Its telling when people can look at "For Free?" and not get where its coming from musically and just think its garbage. You can feel they are working with music people who are trying to make music and not just trends or just making money. I've always been big on who produces an artist. I put that together with cultural assimilation, because its not being passed down much and a lot of that is production. I think this is a world-wide thing though. Everywhere you have people trying to hang onto their traditional sounds, customs, etc, but are battling the mainstream where kids world-wide listen to the same music and dress the same. Everything is melting into a pop sound.
The other side is the money push. The money side is different(and better for artists), but that means other sources of money becoming prominent to those who want to exploit it. You can't have a Wu-tang selling M&Ms. Sprite was as mainstream as it used to get for rappers and those ads were for the "urban audience". Now everyone sells, and you have to be in the middle to do that.