We'd all like to know the future of stamp collecting, but the truth is we really don't know. It's fine to cite other activities that were popular but aren't anymore, cite statistics about stamp auctions and online sales to show the hobby's vitality to help predict what will happen with stamp collecting, but we really don't know. I think we can agree that stamp collecting is changing -- even if we can't always agree on what those changes are.
In fairly recent history (1950s, 60s) stamp collecting was a widely popular hobby served by stamp stores and mail order companies. Albums and stamps were widely available in retail outlets. There were many stamp clubs, many children took up the hobby, many prominent and successful adults collected stamps. "That" version of stamp collecting no longer exists even if some parts of it do. I live in Los Angeles, an urban area of 10 million people, and I don't know of a single stamp store anymore. There are lots of stores, however, which sell video games.
What we generally have today is a somewhat different style hobby: stamp sales online instead of in stores, fewer young people going into the hobby (too much video "gaming"), and an aging of the hobby. But we also have very active stamp sales on
ebay and through mail order dealers. I buy stamps (and albums!) from the UK and Europe and sometimes even from Asia. Most collectors didn't do those things before. I have far more choices of albums than before due to online selling. I'm a member of many stamp societies whose journals I get, and I read a number of online stamp blogs which never existed before. That's not a hobby that's in its death throes. But it is a different hobby from fifty years ago.
Stamp collecting began in the later 19th century. The first published stamp albums date to then. There were stamp societies, journals, dealers, and shows. In the 1930s and 40s, stamp collecting had its greatest growth era. The Great Depression led more people to take up collecting as an inexpensive form of recreation they could enjoy. It was like going to the movies (which also boomed in the '30s) -- cheap and fun and something you could do alone. By the 1950s and '60s, stamp collecting was a widespread, popular hobby that coincided with the Baby Boom, and a lot of those kids "boomed" the hobby. Many of those kids are us today.
Today the number of collectors is no longer growing. But I don't think stamp collecting is "dying". Instead, it continues with changes. Stamp publications, never very large in their circulation, have mostly disappeared. Collectors remain older, primarily white, males. Stamp prices may level off even for good stamps, a development likely to be popular with many collectors. For some collectors today, self-printed albums replace preprinted albums, an interesting change. And unlike in the U.S., There has been a boom in the number of collectors in parts of Asia, China for one. In those countries, stamps are often seen as a way to invest, to store your money against currency problems. Statistics about the number of collectos often focus only on the U.S. or the West. I'm not sure that makes sense.
I think stamp collecting will still be around in 50 years. Maybe it will be a smaller hobby. And it will be different. Maybe stamp magazines and newspapers will be gone. Maybe stamp clubs and societies will be fewer, and maybe there will be fewer collectors. But that's not the "death" of stamp collecting. It's change like sales moving more online and away from brick and mortar stores with their high overhead.
A few years ago there was a widespread belief that computers would soon kill books. Libraries might even die. Book sales would drop. Bookstores would go out of business. That didn't happen. More books are sold today than before, readers still prefer paper not screens, and libraries (and many bookstores) are still around. Reading and book sales did change, but computers did not kills books. That's what will happen to our hobby, "change" not "death".