It's fairly long and the sources quoted aren't necessarily "authoritative" in my opinion (the Four Year Cycle attributed to Ken Hite for example is one I'd never heard of before and doesn't represent the experiences of myself or most of the gamers I know) but it does raise some interesting points. Read it in full at the link above.
The most interesting quote from the article in my opinion is below:
OSR-style games currently capture over 9 percent of the RPG market according to ENWorld's Hot Role-playing Games. If you consider the Fifth Edition of Dungeons & Dragons to be part of that movement, it's nearly 70 percent of the entire RPG market.
The OSR has gone mainstream. If the OSR stands for Old School Renaissance, it seems the Renaissance is over: D&D, in all of its previous editions, is now how most of us play our role-playing.As was pointed out in the comments section of the article, the numbers quoted are based on discussions at ENWorld, not actual sales. ENWorld has a higher % of D&D players than the hobby over all, as it is by it's history and nature primarily a D&D site. I think Paizo may disagree a bit with the market share assumed above. I also take issue with lumping 5e in with the OSR but maybe thats just me.
Now, if we look at Roll20's 1st Quarter usage numbers, we get the following:
See how 5e has more games but less players than Pathfinder? I suspect that's due to "New Game Excitement" effect.
AD&D / OD&D / OSR adds up to 16.49 % of players (obviously folks can vote for more than one game / category) - AD&D on it's own is over 11.5%. As for the share of games run, the numbers only add up to 3.19%.
Only in the RPG hobby would one consider success as death. Or dismiss something because another game borrowed from it. The OSR is less about the rules and more about the products you use those rules with. Until 5e goes OGL or some such, the OSR is where the real innovations will lie.