Are hip-hop and rap the new rock?

A lot of recent hip-hop and rap music seems to deal with issues of race, especially since most of the prominent artists are minorities, mostly black, but most of the consumers seem to be white. (According to Wikipedia “70% of hip-hop is bought by white kids”.) The strong feeling of a unique culture created by and around the music, along with the sexual, racial, intergenerational, and political themes in hip-hop and rap make it seem to me that these genres are playing a similar role in today’s society as rock’n’roll did in the 1950’s and 60’s. I don’t listen to a whole lot of rap, but the two songs that stick out in my memory are below.

White America – Eminem


Changes – Tupac


Whereas it seems to me that rock has shifted to being less political and rhythm based, and more like ballads. (Although there’s still some that makes social statements: The Offspring’s “The Kids Aren’t Alright” http://www.youtube.com/watch?v=u4-aUiddpUo and Ben Folds’ “Rockin’ the Suburbs” http://www.youtube.com/watch?v=QlGCTWL6djo) But even the political rock songs seem really softened/toned down compared to the rap.

My question, then, is:
Is rap playing a similar role to that of rock music, or is it different? Does rock still play a similar role today as it did in the 1950’s?