It'll NEVER die completely, or at least not for a good few more decades or centuries anyways I'm sure.
Funny thing is, before the 1950's, record companies wouldn't touch Rock bands with a 10 foot pole. Then when they saw how much people were loving it, how big it was getting, they of course rushed to sign bands and artists. It remained very popular and evolved over the decades. During the 1980's, Hard Rock and Heavy Metal(Metal and all its subgenres are ultimately just subgenres of Rock) ruled the airwaves, and to me the 1980's are easily the best years. All the guitar heroes, all the flash, all the energy, and so on. My personal opinion is that most "real" rock was killed in the 1990's, though it's coming back, and though it never really died in Japan and parts of Europe.
Now, what REALLY makes a band "Rock" at the end of the day? Everyone has their opinions of course, but I'd say one of the main things is being very guitar driven, usually distorted guitars(though not always) Also, though people don't want to admit this, but flash, image and attitude pretty much always have been a huge part of Rock from the Elvis days. I mean I don't care what anybody says, s**t like Kings of Leon is NOT Rock, and most "alternative rock" I consider to be pure s**t that a bunch of rich white kids/college douches tend to like. So yeah, all this s**t like Kings of Leon, Nickelback, Dave Matthews Bands, etc... I mean a lot of it hardly is all that guitar driven at all aside from a bunch of douches strumming acoustic guitars and wearing everyday yet trendy clothes, acting all polite and s**t... where's the attitude, flash, aggression, and so on that rock is all about? I mean honestly. I don't consider it "Rock" at all and most "alternative rock" bands to me, are a complete Oxymoron.
A lot of the people here saying s**t like "Green Day isn't rock" or whatever else seem to be the types of people that will automatically dislike something JUST because it's mainstream and popular(though they wouldn't admit to doing this) Now I'm not the biggest Green Day fan though I like some of their stuff, but I mean their music is very guitar driven, so it'd be pretty dumb to say it isn't Rock if you ask me. It sure as hell is more Rock than Kings of Leon.
A lot of the older original rock bands I love... George Thorogood, Steppenwolf, Jerry Lee Lewis... stuff like that. 60's and 70's stuff... I like David Bowie, The New York Dolls, Blue Oyster Cult, 80's stuff is my favorite... Iron Maiden, Judas Priest, Dokken, Winger, Poison, Motley Crue... 90's stuff can generally suck deez nuts though in the 90's in Europe lots of good metal subgenres started to come and gain popularity.. idk I'm rambling.