This isn't some idle speculation. Linux, FreeBSD, Apache, PHP and others depend on the wide and varied developer community in order to grow and develop. People who helped got some 'Net notice, their names in the contributor lists and a warm fuzzy feeling that they were helping the effort. But now people are seeing companies and individuals making staggeringly large amounts of money, and are asking "When am I gonna get mine?" Not that they were/are "in it" for the money alone, but, after all, they think, "others are making major bucks." Some other developers are asking themselves why they should put forth so much of their own time and effort to simply benefit the corporate bottom line of a company that, they feel, has deserted the common Open Source contributor.
Of course, that's not totally true. Usually the company implements a "Directed Shares" program that allows significant Open Source contributors to purchase shares at the pre-IPO price. Still, things have not gone smoothly in these programs, with last minute changes in pricing and implementation causing even those "chosen" members to scramble about. And even if you did get in on the 2 big ones, RedHat and VA Linux, and had the money to buy the maximum amount of shares, and cashed in at the best possible time, you would have made about $150,000 (before taxes). Not exactly chump change, but for people who have put 4 or 5 years of significant effort into Open Source, the payoff may seem a little small.
So what will happen? Well, I'm certain we'll see a weeding out of some developers. Some will leave in search of obtaining some of that money out there. Others will leave because the playing field has changed, and recognition by your peers may no longer have the attraction that it once had, what with gobs of money floating around. Others will "follow the money" and start contributing to Open Source in hopes of "getting in" on the action, maybe even dropping any efforts on such projects where there are no perceived fiscal payoffs: "What, they aren't going public soon? Forget them! I'll work on Foobar."
And there will be some of us who stay because, well, even though the world may have changed, we haven't. All the things that made contributing to Open Source are still valid and vital. And so while we may look a little enviously at the stock market pages, and have to endure people asking "Why are you wasting your time" or "Why aren't you rich yet", we stay the course. Sometimes rewards are more than what you see on a bank statement; it's a warm and pure satisfaction that goes deeper than your wallet.