Ah, OK. I think the Obsidian Portal info is reasonably useful, even the most reliable source I've seen so far, although moreso within D&D and less so for other games - I just don't see a larger percentage of Exalted players, for instance, using Obsidian Portal.
So adding up those numbers:
Old School: 3%
3.X (incl Pathfinder): 33%
4e: 49%
That's only 85% of the total. If we translate that to 100%, we get relative percentages of D&D players from Obsidian Portal:
Old School: 3.5%
3.x: 39%
4E: 57.5%
That's pretty close to my initial guess of 10/32/58. Another area it is probably inaccurate in accounting for is the number of "Old School" campaigns, because Old Schoolers are probably less likely to register an online campaign. I don't think this would make a huge different, but maybe a couple percentage points. I don't think we need to adjust 3.x or 4E too much; so here's some rounded off numbers:
Old School: 5%
3.x: 40%
4E: 55%
Now if you are WotC you simply have to take that 40% seriously as a potential market for 5E. The 5% Old School probably won't change and most of it is comprised of people that never switched over to 3E. But in the early years of 3E, there was almost certainly not such a larger number of people playing earlier versions of the game; I would imagine that, two and a half years into 3E, at least 80% of active D&D players were playing 3E, if not 90%+, especially considering that 3E brought a lot of people back to the game.
So relativeto the game itself, 4E is far less popular than 3E was. This is not news, of course, but it must--or should--inform WotC unless they are satisfied with a downsized market. If and when 5E comes out it will be interesting to see how many 4E holdovers there are. I imagine there won't be a lot; assuming 5E is able to draw some 3.xers and most 4Ers, we could end up with a strange grouping like so:
2015 Speculation
Old School: 5%
3.x: 25%
4E: 10%
5E: 60%
This is one of the reasons why WotC must create 5E with 3.xers in mind. Most 4Ers will move on simply because it is the latest version of the game, and The Shiny Is Good. But unless 5E addresses some of the major criticisms people have of 4E, 5E will only further fracture the market.