I'm in my mid thirties as well...I have been collecting and stacking since I was in my teens. I was at an estate sell yesterday where some coins were being sold. The coins were all sold to 60+ year old gentlemen who paid too much for them in my opinion. I didn't even bid. I think there is a lot of serious collectors that never frequent coin shops or shows. The only coin shop that was in my town closed around 7-8 years ago and to be honest I really don't even miss it. As e30kgk mentioned above I think you can find better quality and selection online and have the items shipped to your door step for free. You can't accurately predict the number of coin collectors and stackers there are strictly basd on the amount of traffic in coin stores and shows. I think we will continue to see an increase in online sells and a decrease in shows and LCS's.
On another note...I think we will see even more collectors as collections continue to get passed down to new generations. Sure some will take the collections and sell it but others will get "bit" by the collecting bug.