Gallup has come out with a new survey that tries to estimate the percentage of LGBT Americans and arrives at 3.5% nationwide. If those numbers are accurate, this would mean 60 gay NFL players, 42 in Major League Baseball, 34 in the NHL, 26 in Major League Soccer and 16 in the NBA, based on current roster size, for a total of 178.
Of course, no one has any idea what percentage of a sport has gay athletes and Gallup's survey is of people who self-identify as LGBT, so the numbers can clearly vary. My guess is that 3.5% nationwide is a floor, not a ceiling, and that the real number is higher, though I have no idea by how much.
The projections for sports are important, though, since they give a frame around the issue. If only 1% of the players in the NFL were gay, that would still mean 20 men. Since the sports world would go crazy over one coming out, imagine if 20 did?
It also shows the importance of straight allies in sports. Even if every gay pro athlete came out, they would still be greatly outnumbered (in the NFL, it would be a 1,636 to 60 difference). This is why it was so encouraging to see the show of support from pro soccer players after former U.S. National Team member Robbie Rogers came out as gay.