If you've watched any show like Pawn Stars where people attempt to sell their antiques, you've probably seen someone hawking some tin toys from the 30's or 40's. The seller is likely coming to the table with a lot of assumptions. First, they'll be thinking that vintage toys are hot. Second, they'll draw the conclusion that the more vintage something is, the better. That's usually the way things work. Finally, things only get more valuable with time. Then the shop owner has to deliver the bad news. Those toys have actually gone down in value. The people who played with them as a kid are either no longer collecting, or they have gone to the happy hunting ground in the sky. The demand simply isn't there anymore.
As we are all collectors, we've likely thought the same thing for Star Wars toys. As we age out of the hobby, will there be enough demand to keep it afloat? I want to fork this into two discussions. First there's the modern 3.75" line that we all collect. I think there will be enough demand for the product for a while. Tyler from the SWTVC Instagram group is younger than my Mötley Crüe Dr. Feelgood concert tee, but he's as passionate for the scale as anyone. I don't think that the consumers of the modern 3.75" line are based on age. It's not only the domain of middle aged men and women who once played with the Kenner 3.75" line. I view it as the hardcore fan line because of the world building it affords. Casual fans, of which there are more, will flock to the larger scales, but hardcore fans, who will always exist, will want the scale that allows for Sail Barges, and Shuttles, and Ghosts. The fewer hardcore fans make up for their lack of numbers with their fanaticism (i.e. we buy A LOT).
So that leaves the vintage Kenner line. We Gen X-ers and early Millennials are the ones who played with them as a kid. Will the market for the vintage Star Wars toys see a similar pattern as those toys from the 30's and 40's I described above? First of all, there's no signs of that showing up yet. Values are still going up. It's crazy for me to think that a mint condition Kenner farmboy Luke could be had for around $10 in 1995 when the modern line launched, and now that figure would cost upwards of $200. Part of that could be that the supply of high quality items is shrinking which would offset any loss in demand. 30 years is a lot of time for those mint Lukes to yellow and suffer broken saber tips. But I don't think that's the full answer. I believe the vintage Kenner Star Wars line will remain collectible so long as Star Wars has pop culture relevance even if those that played with the Kenner toys have moved on to playing pickleball or are pushing up daisies.
My reasoning is from looking at other collectibles in the pop culture arena. Anyone who read Amazing Fantasy 15 when it was published would have been born in 1957 at the latest. The collectibility of that comic is off the charts, and I don't think it's the 67 years olds who read it as a kid that are propping it up. I doubt it's those jet setting nonagenarians who are keeping the T206 Honus Wagner cards in seven figure territory. It's more likely Gen X tech billionaires doing that. If we want to stick to toys, Ideal's Batman Utility Belt from 1966 sold for $16,000 a few years back. I highly doubt it sold to someone who played with one as a kid. My money's on Kevin Smith. The difference with those tin toys from the 30's and 40's is that they are not tied to an IP, or the IP is largely dead (Buck Rogers). If the IP is not dead, the collectibility is still there. Disney toys from that era still have massive demand despite the original target demo having converted to worm food a while ago.
I don't think 3.75" Star Wars is going anywhere even when my generation matriculates down the field. The modern line has value unto itself as the world building scale, and the vintage line will have collectibility as long as the IP stays relevant. Collectors like to get close to the origin of their hobbies, and for Star Wars toys, that is, and will forever be the Kenner line.