I talked to a guy that works for a HD dealer there 500 and 750 bikes are not selling too well. This means the under 40 age crowd are not getting into motorcycles to replace the aging bikers that retire from riding.
I agree with you except for the bit about the under-40 crowd not getting into motorcycles. What they are not getting into are cruisers, and many of those people who bought those big cruisers from the first decade of the 2000s are too old now to want to continue riding these huge monsters (including the VTX 1300). I bought my VTX 1300 from a man in his 60s who wasn't interested in continuing to ride this beast.
I don't know what the total sales of MCs are to the under-40s but sportbikes and naked bikes (naked bike = sportbike without fairing and more-vertical sitting) are plenty popular here and it's what the under-40s are buying. You only need to look at the mega monsters that the likes of Kawasaki, Suzuki and Honda are putting out these days in these two MC categories (sportbikes and naked bikes). Heck, even Honda has finally updated their liter Fireblade bike.
When I was at the Honda dealership, I saw a girl in her 20s with a Honda Grom. They've sold them out, all their Groms. Sold out before even reaching the dealership. The Honda Groms are also extremely popular in the USA even though it's a 125cc bike. The younger folks are buying bikes, but they are buying bikes that are good value for money. To put a recent example of a cruiser no longer made for the European market: a +700lbs cruiser priced at 16,500 euros (over 18,000 US dollars) like the Vulcan 1700 Classic (no bags, no nothing) is not good value for money. Drop the price to 10,000 - 12,000 euros and maybe then we can talk.
I've heard it from several dealerships from the big 4. In Europe, the Euro 4 legislation has killed any possibility of bringing back those monster V-Twin cruisers and tourers. Legendary bikes like the Vulcans, VTX, Shadow, Intruder or V-Star are all dropped and will not be made anymore except for a couple of bikes under 1000cc. Bikes sold here for the under-40 crowd are getting smaller except for a few exceptions in the legandary liter-sportbike category.
You guys in the USA still have the aforementioned Kawasaki Vulcan 1700 which is an awesome bike. Unfortunately, Kawasaki seems to think that their bikes can be priced at Harley prices, so they're priced expensive and they were very expensive in Europe when they were selling them here. Their Voyager was priced the same as an Electra Glide (or whatever the name is for the fully-kitted tourer in their model range) and the Vaquero (called the Vulcan 1700 Custom here) also had a stupidly-high price. Seriously, Kawasaki? No wonder they only sold single digits of those.
Very few people are going to pay over 20,000 bucks for a motorcycle. And, if they are going to pay that amount, they sure as heck they're going to buy a Harley for the name only (or a Goldwing if they actually ride). Harley can get away with stupidly-high prices because of their name, not because the bikes are actually worth that price objectively.
Going back to the Kawasaki Vulcan 1700, had it been priced accordingly here in Europe, I'm sure they would have sold many more. But plenty of people have complained of their pricing. I'm sure that, if the Vulcan 1700 platform was more popular, Kawasaki would have acted to make their engines compliant with the Euro 4 legislation. But, no, Kawasaki thought they could get away with their Harley prices and failed miserably. They failed so hard that they killed the entire 1700 platform for the European market. We're talking of a bike which is hands-down better than a Harley Davidson bike, yet they're happy to throw it all away because they can't sell them at Harley prices.
Euro 4 legislation + high prices + mandated ABS brakes on all bikes made + under-40 crowd with no money = no selling of big V-Twins in Europe.
It's a shame to see all these legandary bikes go. Some of these bikes had decades of history. How I wish they would bring back the Vulcan 2000 or VTX 1800 with ABS included. Not going to happen ever.