What I don't think OP realizes is two important points:
- computer hardware depreciates at an alarming rate (without bitcoins help)
- bitcoin is DESIGNED to depreciate hardware used on it (by virtue of difficulty)
So to this end, I think the future of mining is going to be in the favor of the casual home user who buys a GPU as a multi-tasker, to both play games and then mine for bitcoins while it's idle.
The exception here is that the OP is underestimating the general public's reasoning abilities. I use projects like Folding@home and SETI@home as examples. These projects are advertised to "use your computers spare cycles", without also admitting by virtue of your computer being on, it's costing you money. So every month, *@home users are donating $20-$30 to a project of their choice by proxy of their power bill.
AND THE KICKER here is that people do this for $0 in "in pocket" returns!
So as long as bitcoin can make someone $0.01 in pocket, people are going to mine. People won't necessarily INVEST in new hardware specifically to mine, but people will continue to mine.
If you visit the BOINC stats sites and check the world top 100 crunchers and their rigs, these people have crunching farms. They spend hundreds to thousands of dollars a month without any $$ returns, all for the sake of becoming #1 and staying #1. Most crunch just for the stats, but their are lots who crunch because they believe that the project can help mankind in the present or future. I crunched for World Community Grid for 5 years due to their Cancer Research projects and only stopped because of the the monthly increases of the power cost this year (about $0.01 per kwh increase a month). Like last February the power cost was only $0.18/kwh, now its $0.26/kwh (geothermal power was supposed to be cheap
. The power company even charge the cost of stolen electricity to all their consumers. Add to that cost of maintaining the rigs, just last month I lost 2 power supplies, 1 motherboard, and 1 UPS due to power outage/surges/fluctuations. Power surge strips didn't help. There's only one power company in our area so there's no choice but to accept their crappy service.