Not All Great Ideas Work
I'll admit, I like the idea of open source intellectually—the free exchange of ideas, innovation through collaboration, and the prospect of being able to "fix" those annoying quirks that every software package contains. Will open source overtake commercial software development? I don't think so. Ultimately, every developer needs to be compensated for his or her work. Could developers freely give away their labor? Sure. Is any one person likely to work for free forever? No—unless he can get a job that pays him to give away his code.
Has there really been an impact on the commercial vendors because individuals or companies are flocking in droves to open source products? Admittedly. Has there been a significant impact on the commercial vendor's bottom line? Perhaps. Unfortunately, there's not a lot of data on what could have been. What we've seen is that the dominant software vendor is still growing by leaps and bounds, dragging along the others in that industry. The same people who are intrigued by the idea of open source will continue to use OpenOffice.org, Apache, and Linux. While it would be wrong (and foolish) to state unequivocally that open source doesn't have a future, I don't see the disappearance of commercial software development. The only argument I've seen in which open source could potentially be of value (assuming that I could get past the fact that people are giving their labor away for free) is in "commodity" software. An article written by John Newton, CTO of Alfresco, presented the idea that the open source software development model is for packages where the functionality has matured to where there is little innovation left; these packages don't contain revolutionary or innovative features and the software could be "cheaper" if the overhead of high-priced R&D budgets and high-cost developers were removed from the equation.  For truly innovative software development, where the developers have made significant advances in a new area, commercial vendors will likely continue to dominate. As Newton points out, innovative software development is expensive and the sale of commercial software is the only way to support that kind of development (Microsoft's $7 billion research and development budget is evidence).
Finally, unless you or your company can support developers to maintain open source software, let someone else do that. You're going to pay one way or another. Whether you pay for support or a license to use software, money is flowing from your checking account to someone else's. At least when I buy a commercial software package, I know who's producing the software—if something is wrong, I can pinpoint who to pursue.