Ten years is to far away to gauge imo. To many things can change so many factors. Wars, shitty economies, gov regulations and many others.
I think taken a look at the next 3 years is a better approach.
3 Years -
Tubes will have replaced most of the mgps/tgps out there. They will by then be tweaked to earn good net revenue from promoting themselves (dvd archives, "free" life time access etc) or promoting programs that have the best products. Most are making good profits as we speak, but they will be even more tweaked as time goes on.
The industry's over all sales will be down from where they are at today. Due to the US still being in a bad spot. This could actually go either way, but by the looks of the way things are now I don't see the US doing good for another 5 years and at that time people will start spending again, more joins will flow in as a result.
Most of these 10-50 join a day programs will have been purchased by bigger fish. The industry will mainly be 10-15 companies and they will be doing all the joins (maybe even a smaller group of 5-10). Sure a pool of programs will be around doing 5-20 joins a day but with all the stress and work it will take to compete with the bigger, more solid companies will force them to sell. That or get into some thing else and watch their program die soon enough.
Small webmasters will still be able to earn cash but nothing like before. By 3 years time getting into adult and making million will take a lot of cash backing the project + a ton of experience, stamina, staff, and a solid webmaster base.
As far as the original question where do I see the biz in ten years- It will be here and always will be. Move with the times and you will make cash for sure - question is how much.. No one can say
Lets wait and see.
Ant