It seems this thread got just a little bit hi-jacked off-topic.
I don't believe that the scanning hobby will ever end. Regardless of whatever new technology comes along, in most cases, there will most likely always be the matching technology to allow us to monitor it.
I also believe that there are some services that will never go digital or encrypted. One has already been mentioned earlier in this thread-aviation. Because commercial aviation is international the radio systems have to be identical worldwide. To switch commercial aviation to any thing other than the AM mode they already operate in would be unthinkable. Another great service to monitor are the railroads. Since all major US railroads interchange not only with each other, but with Canadian and Mexican railroads, the FRA (Federal Railroad Administration) has mandated that all locomotive, and train crew handheld radios be capable of operating on the 160 MHz band allocated to the railroads. The only change coming to railroad radio is the narrow-banding, essentially doubling the amount of available frequencies to the railroads, which has to be done by 2013. Just like in aviation, the cost to the railroads to change to a totally new radio system would be extremely cost-prohibitive.
As for public safety agencies (PD/FD/EMS) many will embrace the new technology but I believe many will not, and for various reasons. As this thread was started to ask about the future of scanning I will not reopen the box of worms that has already been opened earlier in this thread. Just as when trunking and APCO-25 came along, and were reported to be the end of scanning, we found out 2 things:
1) Not every radio user went trunk or APCO-25
2) The scanner manufacturers came out with affordable scanners that could monitor the new technology.
There will always be something interesting to listen to on our scanners. Suffice to say that scanning will always be a hobby, definitely in our lifetime, and I'm sure for a while yet beyond that.