It will always be around, just like blues, bluegrass, jazz, classical, swing and other genres are always around.
But, like the other genres, it won't be the dominant genre. In fact, the only reason it lasted as long as it did on top was because the primary market for it was the single largest population bubble in our history (the baby boom).
Yes, like some of the other genres I named (remember the "swing fad" with Brian Setzer, etc., or the "bluegrass revival" after the release of "O Brother where art though"?) it may have brief periods of resurgence at the top of the charts. And it will always have fans. And like classics of other genres, certain albums and artists will remain popular (Beatles being an obvious example) even if the genre isn't as a whole.
However, the demographics are all wrong for it to stay on top forever. It was the pop music of a particular age group (the boomers mostly) and that age group is now middle aged or even senior citizens. They aren't buying records anymore and eventually they'll all be dead.
And as a result, rock will be just one more "niche" musical product with some other genre as the best seller.