Not necessarily saying the electric guitar isn't dying, but the economic argument isn't very convincing. There are a lot of guitars in the world now and we keep making more, consequently people aren't prepared to spend as much money on them. The people who are willing and able to spend $1000 on a new Les Paul or USA Strat are an aging generation for sure, but maybe their grandchildren are just playing guitars that cost $200 instead? You can get a pretty decent guitar for peanuts these days - I bought a perfectly playable strat copy for like $40 (actually 30GBP) off Ebay a while ago, with a (small, tinny) amp thrown in.

I've been expecting the death of the electric guitar since the '80s, but it seems surprisingly resilient.

Edit: In addition, although I'm incredibly old and don't claim to have my finger on the pulse of the zeitgeist, it seems to me that in the post White Stripes era playing shitty second user equipment is widely considered cooler than playing expensive new equipment.