Interesting thread. Agree with a lot of points that have been posted especially the following in no particular order.
High entry cost for kids to get started in the hobby
Demographics
Cyclical nature of the hobby
Economy
Different sports competing for the interest of today's youth. (soccer)
Personally I left the hobby in the early 1990's as it wasn't fun anymore and I refused to pay over $1.00 per pack for new cards. lol
I returned to the hobby in 2008 as cards I have always been interested in, (pre-world war II) seemed to be decent values when found on the internet.
IMHO, some things that will help the hobby..
Internet- ie message boards
Integrity or some form of policing in the hobby--in some ways I think that card grading helps the hobby. (I realize there are some cons to grading as well)
A marquee player who can capture the nation's attention ie Jordan in the NBA
Oddly enough a return of wealthy investors purchasing high profile cards in which the purchase makes headlines.
Just my two cents on a rainy day in my area.