There will be new things in Rock, but they won't take over and dominate in the same way that say, alternative did in the early nineties... the marketplace is so broad and diverse and everything and anyone can find an audience on the internet these days, regardless of distribution deals etc.... sure the big players that have big record deals have a sizeable advantage, but its not insurmountable anymore...
Plus there are so many genres around now its a real mish mash without any particular genre being dominant as far as i see it... there isn't a real divide in music, most people will and do take a little from column A and a little from column B in their tastes.
IpoRAB, Mp3 players allow people to dabble in music more instead of buying ful length albums and making a commitment to an artist or style...
So its all very post modern and diverse and i think to talk in terms of next biug things is sticking to an already irrelevant view of how the world of music and its distribution, and how people consume it works...