Ten years from now? Hmm... well, look at how fast mobile internet devices are gaining marketshare. Even in third-world countries. People are carrying around blackberry's, iphones, ipads with data plans, android tablets/phones etc. The internet won't be the death of the WTBTS, but it will continue to bleed it's numbers and give exposure to them.
Now what I see happening...
The current Conti case goes through it's appeal process, losing, the gain even more bad press, and more money to pay the damages. In the meantime, more people will come forward with abuse cases, possibly another Conti, maybe a couple more than that. These will be huge hits to the WTBTS warship.
Growth will come to a drip. Not even a trickle. Western countries will start having its growth stop and reverse. I can see them hitting 8 million and hover for a few years while more abuse cases and gaffe's continue to blow holes in their ship.
I could also see them getting taxed in this time. Another financial hit.
Another change to blood transfusions. New light stating it's a conscience matter. This would be a huge hit to their ship as well. Lot of fallout.
I see a huge doctrinal change coming. Either with bringing in a new GB member that is charismatic and or the three "commanders" of the GB sticking the ship into overdrive, more hardline, more paranoia, more propaganda per usual.
The change to DC/CA will happen in the next 5 years I think, 2 day DC, 1 day CA whether they keep the SAD or not doesn't matter but I see that going away in ten too.
Everything is now downloaded to your tablet and bring that to the meeting to study along. Maybe some app for tablets from iTunes or Android market that lets you download and donate all through the app store. This allows selling of the print machines and only keeping enough to print for the 3rd-world countries.
Conventions/assemblies are now only in assembly halls. No public venues.
I also think WWIII will happen sometime in the next ten years, throwing some serious "trials and tribulations" for the witnesses.