People know rock and roll by the trends. What happened in the late 70's? punk. Early 90's? grunge. Pop was always at the forefront at the charts, but this has developed little, and people don't remember eras for their pop, so I don't count it.
I'm known among my friends and even my bandmates as the 'music man' not for ability but for knowledge of the history, present and future of rock. And when they ask me what the current trend is, there's no simple answer. I had 'ummed' and 'aaahed' over this for a while. Sometimes I wouldd think 'rocks going simple and stripped down, we've got The Vaccines, Two Door Cinema Club and The Black Keys producing major albums'. But on another day I might think to myself 'complexity and development are on their way up, look at Radiohead's new album (TKoL) and Arcade Fire. As well as this Indie is becoming more layered with Foster The People and the XX'.
The list goes on. Sometimes I thought nu-folk is what future generations will remember (Laura Marling, Mumford and Sons, Fleet Foxes) and sometimes it's the integration of electronica into guitar rock (Bloc Party, Klaxons, The Dead Weather).
And after all of this thinking I realised how simple it was. Times have changed. The era of 'trends' of music is over. Everything is happening. There is still someone making music in every genre if you just look hard enough. People who complain about the state of music now are just lazy. Music will never be exactly the same as it was ten years ago, but that doesn't mean to say that genres will die.
There are a lot more bands then their have ever been in the past, which means more people to push the boundaries of what has been done before.