I agree with others that the Botanical Gardens show is not really about the trains, it is about the conservatory being decorated as a winter wonderland with the theme being NYC buildings and such (the conservatory itself is quite a jewel, I was married at the Botanical Gardens several decades ago. I don't think the mobs of people there are there to see the trains per se; on the other hand, even if only a couple of kids or adults gets interested in trains from it, all good.
I also tend to agree that toy trains are going to be around for a while, it could be in very different form, but it will be around. The market has faced its challenges, back when Lionel was on wobbly legs and then MPC took over, it didn't look 3 rail O would survive. Yet we saw after that period a lot of unexpected things, we saw Richard Kughn basically revitalize the brand, we saw MTH and Atlas enter the 3 rail market, along later on with Weaver and 3rd rail, we saw the invention of command control where 3 rail (to me) outstripped scale...and none of that was expected, dirges were being sung about 3 rail every year.
Yes, this surge was partly because of baby boomers getting nostalgic, but that was only part of it, and that part is waning as boomers get older. However, part of that surge was the scale modelling, it was because of the detailed products and the command control (and now radio control), and I think that part is going to be around. Just based on my experience in the hobby, among the younger people in it, they tend to be attracted to the command control and the more scale elements, and it is what I would expect. Yes, smart phones and social media and the like pose a threat to this, but so did TV in its day, TV was often cited as one of the main reasons for the demise of Lionel in the 1960's for example....yet a lot of those kids who were 'ruined' by tv (you know, all those little serial killers dropping anvils on people's heads and all the other mayhem found in Bugs Bunny and the Road Runner!) came back into trains as adults,and not all of them had trains as a kid. I grew up well after the golden age of trains, by the time I became aware of things trains were either commuter rail or were struggling freight railroads with Amtrak kind of a curiousity, I never saw a steam engine in active service, never saw the great long distance trains, but still loved trains (actually, real trains hold an interesting parable to our story here, experts were predicting that long haul trucking and air shipping would wipe out the railroads, that they were more efficient, etc...and like with 3 rail O, real trains underwent a kind of revolution that the 'experts' didn't see coming).
It is all great and good to rumble about young people being couch potatoes with no brains,texting and doing who knows what on their phones and tablets, how they don't appreciate 'real things' like trains, but what that leaves out is that young people always have a ton of other things they are interested in and a lot of cranky older people blaming them for the end of civilization..and I think going down the road some of those young people obsessed with phones and whatnot (the way young men were obsessed with the horsepower of a bored out 327 small block or whatnot once) are going to find the joys of trains. Will be a niche market, may be smaller than today, but it will be around, I am pretty sure.