I think a good portion of our shops will be closed in 15-20 years. Sure, some of us will adapt but I think parts of the pie will just disappear. Here are the threats I perceive:
1. Computer hardware becoming cheaper - everyone will eventually just replace their hardware
2. Adoption of cloud computing - there are fewer barriers to everyone adopting cloud computing. Internet speeds are getting faster everywhere. people are saving files with carbonite and dropbox and slowly starting to trust the cloud. businesses are slowly starting to trust it as well. as soon as security concerns are addressed, there will be an explosion in cloud computing
3. More secure networks - IPv6 has the potential to stop all SPAM and maybe even viruses, malware on an ISP or even Internet level. Viruses could disappear overnight with the next draft and adoption of TCP/IP. The computer world in which we live now addresses security after-the-fact. New systems and protocols are being built with the security in mind up front. Eventually the industry will catch up and eliminate most of these threats
4. MSP industry shakedown - you see how hard it is for a new PC company to start up and gain any sort of market share against Dell/HP/Gateway/Lenovo. Eventually there will be little barrier to Dell or some other company gaining market share of remote computer support or business MSP support. Within the next 15-20 years there may only be a few big players and a bunch of little guys struggling with localized or specialized markets doing business support. As more things go cloud-based and more companies trust remote support providers, it will become easier for the big players to fight over that market share. Who will it be? Google? Microsoft? Dell? someone new?
Basically, I plan on making as much money as I can over the next 20 years and then I hope I can diversify into something else. But I won't be surprised if I only have 10 years left before some of these things seriously eat into my business. One thing that will NEVER go away - Corporate IT jobs. I figure if I stay current I can always go back to the desk job if I have to.