You've made some good points, but I have to disagree with most of them personally speaking of course. Others may agree wholeheartedly.
The first biggest disagreement is the last point you made.
While I appreciate the thought, I have to point out that America is a capitalist society and as such there isn't anything more powerful than the dollar to make advancements. Consider prior advancements in technology. Almost every single one of them was due to financial gain. Weapons and associated tech during every war increase due to the government throwing millions if not billions of dollars at defense contractors. Improvements in all the main stream software applications and operating systems have come about because those companies wanted to make more money. While it would be neat to think that sharing of technology advances things, it doesn't really stand up to examination.However, a scientific sharing of software technology will advance our capabilities far faster than a profit motive can.
The next is that GIMP will eventually surpass PhotoShop. Again, that would be sweet if it did, but realistically it won't happen unless Adobe stops all development. I can see one of two things happening. The first is that Adobe decides that GIMP is becoming too strong of a competitor and reduces its cost (probably a pipe dream), or second it starts incorporating all of the code and advances that GIMP is making (a much more likely scenario). These is feasible since GIMP is open code, and the Adobe developers can make easy tweaks to make it different enough to call it their own. Then of course you have a corporate name and support behind the product. There are very few businesses that would be willing to embrace open source applications within their infrastructure. I fully realize that there are some and have even considered it for the company I work for, but in the end open source applications can be more trouble than they are worth.
I sincerely hope that I am dead wrong and you are completely right but being a realist and having taken many a business class I'm afraid that my scenario is a bit more accurate. However, no one can know for sure and a year or two from now may prove us both wrong when some other graphics program stills the market share. Who knows where Corel is headed or what is in the works currently.