Meh, I don't see our bikes becomeing rare collectible items. Motorcycles don't make very good collectible items as motorcycles are made to be ridden and need to be ridden to keep in form. All it takes is a car jumping a red light to destroy your 1965 Norton "Whatever" valued at 80,000 bucks to kill the bike (and maybe you).
Look at Jay Leno, plenty of weird motorcycles he's got and doesn't know a lot about them either. He's the typical example of a motorcycle snob with too much money. He did get a Vulcan 2000 when they were first made (only because it was the biggest engine at the time) and he hasn't ridden the bike since then. It's collecting dust in his massive garage along with hundreds of other motorcycles and cars. Well, not really collecting dust, as he has people that dust them off regularly.
Take a look at a 1997 Honda VT1100C ACE. Great motorcycle. Reliable as it comes. Decent power (more powerful than the HD bikes of the time). 20 years old. Being sold for 3,000 bucks. Same goes for the Honda Magna's. These were motorcycles that made a spot in motorcycle history for one reason or another, just like the VTX 1800 did in 2001. Now take a look at any HD from 1997 and people buy them for 10,000 bucks because of "history", "pride" and all that nonsense that many HD owners have been brainwashed to believe so as to pay premium prices.
To keep things in perspective, the big V-Twins from Japanese manufacturers that we so much love (I love 'em all) are too fat, too bulky, not very comfortable, handle like crap, vibrate too much (compared to other engines) and will rust fast if you don't take good care of them. Honda had to come up with the VTX 1300 because the VTX 1800 sold so badly. That tells you how much people appreciated a huge bulky motorcycle (i.e. VTX1800) that wasn't even a speed demon.
For the vast majority of people, the VTX 1800, the Vulcan 2000, the C109, the Yamaha Roadliner/1900 are too big for no other reason than being big and that puts off a lot of people and put a lot of people off in the past, which is why they sold so few of them. It was a race of who made the bigegst engine for no other reason than to claim they had the most powerful V-Twin, even if the demand for it was almost none (hence part of the reason of the VTX 1800's demise). Add to that that most people buying cruisers or collectors are not young folks (guys in their 50s and older), and owning 800lbs of bulky of metal that handles like crap isn't really much of an attractive endeavour. The goldwing is the exception, but that bike handles almost like a sportbike and is extremely comfortable.
I love all the above huge V-Twin bikes and I love their tractor-like sea-whale proportions and characteristics. Many of you do too. But we are the minority and part of an item becoming a collectible is that there's a fierce demand for it and too few of them available. VTX 1800s are being sold for 3,000 to 5,000 bucks, as so as are the Vulcan 2000, C109 etc They are now 10 to 15 years old and are getting cheaper and cheaper.
I could see some funky 1970s 1100cc Goldwing becoming a collectible item though (great bike that handled like a dream for its times).