I've enjoyed reading this discussion -- it's certainly an interesting question, and while baseball card collecting has certainly seen a decline in popularity recently, I think it'll always be around. Sure, childhood pastimes are changing and kids are now occupied with video games and Disney indoctrination, but a drive through springtime suburbia will reveal plenty of wiffleball games. My sister babysits the kid across the street from us (he's six years old, I think) and whenever she's there he likes to show her his most recent baseball card acquisitions and flip through his binder. The hobby might be a bit unhealthy, but I don't think it's dying.
I do think that the vintage baseball cards collected by most of the people on this forum are a whole different ballgame than modern cards (pun intended). The people willing to spend thousands on old cardboard is incredibly small to begin with, and that small group might become smaller -- but it only takes two people with money to drive the price of something up into the stratosphere in any given auction. I'm only 20, so I certainly plan to be buying things twenty, thirty, forty years from now, and I'm sure there will be others like me.
Most importantly, there will always be a market for things of aesthetic value and historical relevance, and vintage baseball cards represent both of those things. With any luck, though, the market will collapse and I'll be able to snag a PSA 7 Cobb Bat Off for a couple hundred bucks
