The answer, of course, will be pure conjecture ... but I'm also sure many of you have opinions. So, here is mine. Jump in with yours at the end.
I don't think that IT folks have ever seen themselves as union types. I don't mean this in a demeaning way, but feel free to poll your local IT staff. After you ask them if they would ever join a union, ask if they could ever see it happening. My guess is that many probably belonged to unions at one time or another prior to getting through college (like I did - Amalgamated Meat Cutters and Butcher Workers - I worked in a supermarket and had to join to get the job)... but most would not be able to visualize IT as a union.
Moving past whether it would or could happen, what would unions have done for IT over the past 10 years. Would there have been stronger push-back on H1B Visa's? Would the authorized number of visas be as high as they are right now? If limited, what impact would that have had on the growth of the economy? Would a shortfall of IT workforce have driven up salaries? Would there have been a direct (and negative) correlation to growth - would this have held down innovation? As the economy is cooling and global corporations are cutting jobs, would a centralized union have fought to force firms to cut H1B jobs before US workers (See Senator Wants Microsoft Job Cuts to Target Foreigners)?
While you're chewing on that angle, consider an opposite universe where IT was a true profession. This topic was considered quite recently by IEEE's IT Professional magazine. If IT were organized like lawyers, doctors, and accountants - complete with a governing body, ethics, standards, licensing, etc., how different would the US business landscape be today? Imagine a world where IT employees and consultants required a license. Would the workforce be smaller? What would happen to salaries? Would our profession allow licensed and apprentice levels to fulfill the required staffing of firms?
Again, moving past if/how it would happen, where would we be right now? Would a professional board have objected to international resources? Probably not, as long as they met the requisite skills and paid the full fees. Would a professional board have used lobbying to control and direct legislation to assist the licensed membership? You bet. Would licensed professionals result in higher quality performance, standardized capability, and higher output? I would expect a professional body to create standards and quality... but I don't know that true professionalism would necessarily create higher output. Would making IT a profession attract more US students to pursue IT as a career? I would think so.
More importantly, what do you think? Jump in and add your 2 cents. I truly look forward to your responses.