It's not as if there haven't been many forms of the "Rock Is Dead" rant for decades now. For instance, see producer (
cough "engineer"
cough) Steve Albini's diatribe on the subject from back in the early '90s, "The Problem With Music":
http://www.negativland.com/news/?page_id=17
Rock music has become more niche as the recording industry has moved away from the old model of AOR and LPs, where there would be a few good singles on a record at best, to the new model that streaming music has enabled with songs standing on their own merits, and the financial model that necessitates touring and live music.
It seems as if the downward pressure on guitar sales is a money and business problem, not a music problem. There's simply a glut of gear on the market. Reverb and eBay have made it a simple matter to pick up a quality used electric guitar.
Confession: I've been playing since I was 16 years old, and I didn't buy a new guitar (an acoustic) until I was over 30 years old. There was no need to. I could get whatever kind of guitar I could afford, at the price I wanted to pay, in excellent condition on the used market. And I still can. It made no sense for me to buy new. And it makes even less sense when it comes to amps. I know places where you can find a huge variety of amps in good to new condition.
The downward pressure is increasing now as the baby boom generation is retiring or passing on, and a lot of those guys who are still around are thinning out their collection which means many quite nice, well-cared-for instruments are coming onto the market all the time.
Richard Ash says: "Our customers are getting older, and they’re going to be gone soon." Baby boomer guitarists tend to have a lot of disposable income. They're far more likely to cruise right into a GC or Sam Ash store and make a GAS-induced impulse purchase of an additional guitar. But that doesn't change the fact that a lot of musicians don't have a lot of dough, and they're surfing eBay for deals.
Parallel to this phenomenon, the amount of information that buyers have at their fingertips, via the internet, has never been more abundant. Guitarists know more about the instruments than they did in the past. They know what woods, frets, necks, bodies, pickups, and electronics do and will work, and in what combinations they will be optimized. See the "partscaster" hobbyist trend.
After all, an electric guitar is essentially a plank of wood with a bolt-on neck and simple electronics and hardware. If you have one you like, and chances are you do if you're a musician who plays a lot, there's no urgent reason to let it go. If you love how it sounds, you just keep playing it.
On top of all that, there's additional downward pressure coming from the low end of the market, and the improvement in quality of guitars from Mexico and China. Just look at all the love for the Fender Squier line and instruments such as the Classic Vibe Telecaster.
To sum up, I'm not worried about electric guitar music. Rock music has been in a bad place before. In fact, there's been more than one dark age. It's cyclical. If you're a music history buff, you'll know the significance of this date: February 3rd, 1959. It was called "The Day the Music Died" for a reason. Buddy Holly, Ritchie Valens, the Big Bopper—gone. Elvis was in the Army. Little Richard had quit. Jerry Lee Lewis was in career trouble because he married his cousin. Rock 'N' Roll seemed like it was over in the early 1960's—as if it had all been a novelty from the start. The charts were swamped by sweater singers and crooners. The rough, raw, and electrifying music of the late 50's looked like it was gone forever.
Then the Beatles, the Stones, the Kinks, the Who, the Yardbirds, the Animals, and all the other British Invasion groups re-invigorated the genre.
The same thing happened, to a lesser extent, with punk rock, and then grunge.
So I'm not worried about rock music. It's not dead. You can find it if you know where to look.