I am 29 years old. I don't know if that gives me any qualification to speak on the manner or not. I am probably a bias example beings as I was raised by a smith collector, but I have been probed on similar subject matters by other collectors friends due to my youth. Even at my age, it still feels like a crapshoot trying to project what my peers may be into down the line. Here are a couple blanket statements that I tend to make in these sort of conversations.
1. Right or wrong, revolvers are looked at with a degree of novelty to the younger generation. Practicality is almost entirely out the window. A model 14 might be the best thing to punch paper with on range day, but a 3.5" 27 is going to be easier to sell, just because my generation thinks they look cool.
2. I remember 686's on the shelf in the stores growing up, not model 25's. My brother in law is about my age. He is an avid hunter and shooter. If you asked him to rattle off every smith and wesson model he knows, the list would stop at 686.
3. I am high on the longevity of model 29's right now. Dirty Harry was decades before I was born and it has nothing to do with that. I owned a dozen Smith's before I ever saw the film.
There is no reasonable autoloader that provides the same powerfactor. A .357 buyer has the choice of 586, 686, 19, 66, 27, 28, etc. A .44 mag buyer has the choice of blued or stainless (yeah, somebody is gonna come and correct me about the existance of the model 69. Whatever.). The concept of revolvers being a novelty lends itself hand in hand with people wanting to buy a gun that will give their buddies a rise out at the range.
4. Bullseye and silloutte are almost non existent now. USPSA and IDPA are. I don't know that revolvers have enough of a place in modern shooting sports to be weighed heavily into considerations.
5. Red dots and optics are massively popular whether revolvers have a place in shooting sports or not. Some people my age can't shoot without them. Take that for what you will.
6. The average consumer is more researched than ever before. You can bet that posts on this forum will be read and referenced for years to come. What is highly regarded now, is likely to stay that way as those are the opinions the next generation is going to be reading when they are doing homework on the shiny revolver they are looking at. The rabbit hole that is researching Smith and Wesson's is a seemingly unique aspect. I'm not saying there isn't a plethora of information about other guns and manufacturers, but the depth of information, documentation, and overall researchability is second to none from what I can tell. We can thank all of those who spent years documenting these guns, as they are the ones responsible for keeping the values up over the years to come.
If I had to make a single submission to the modern classic era list, I'd throw out the 29 classic DX. Maybe it's not 21st century, but it's well after the P&R era... and I don't do lock guns.