3-D printing, manufacturing of replacement parts for hobbyists (even in small batches) and well narrated instructional videos of how to do repairs will keep them working long past their original life span. Comparing it to old cars, a lot of cars that would have been considered junk or parts only are now restorable because of the new availability of replacement parts and cheaper tools, and shared info on the internet. Jamboxes will benefit the same way.
As for the popularity, I see young kids (like grade school/high school age) who love skateboarding, vinyl records, 80's and 90's looking clothes, BMX bikes, stuff like that, and I definitely get the feeling that once they are of money earning age, they will want to get in on some of this stuff we hold so dear. Price out a square body Chevy pickup from the 80's and see what I mean.
In the same way the 50's got a rebirth in the 80's, the 80's could get the same thing in the next 10 years. And it won't be all older guys trying to relive their youth either. I have a deep love for 50's hot rods/custom cars, muscle cars and midcentury furniture and I was born in 1980. I've been saying for years that 80's modern furniture (think Miami Vice coke dealer batchelor pad, black lacquer and mirrors and colorful neon type ****) will be hugely collectable and valuable in the near future.
And nothing embodies that time period better than a big blocky silver jambox from the 80's, they've got style, they're tied to the music culture and they can be used and shared in a group or party setting, they're useful.
I predict we've got a long way to go up before we come back down again.