It will exist, but won't be massive, won't get much mainstream coverage.
It will seem like it had it's peak years ago.
You'll go to special rock music clubs to find it.
There will be a specific rock music stage at some of the the bigger festivals.
It will be generally something that is listened to by the older generation.
You will be able to go to university and study how to be in a rock band (tho this already exists, which is how bands like The Feeling came into existence).
People will say 'oh look it's the token rock entry' when the Mercury prize nominations come out.