Fact: Nobody won 20 games in 2009.
Question: Has the slide in 20-game winners been not only arrested, but reversed?
Answer: Why are you so obsessed with 20 wins?
That answer is a fair question. Qualitatively, there's almost no difference between winning 19 games and winning 20 games. Since 2006, no pitcher has won more than 22 games in a season. So let's break the winners into groups of three wins: 17-19 and 20-22. For each of the last five years, the number of pitchers who finished in those groups:
The 2010 numbers will probably wind up looking something like 9/4 (give or take). Which wouldn't be appreciably different from 2007 or (especially) 2008. Maybe 2006 and 2009 were flukes ... but I say one's a fluke and two's the hint of a trend.
I suspect that we can partly explain this season's numbers by excellent pitchers working for teams that score a lot of runs. It's helped Roy Halladay and CC Sabathia, anyway. It's hard to win without run support. Consistently, anyway.
The other key to winning 20 games is pitching a lot of innings. And that's not trending positively. Halladay and Sabathia and Felix Hernandez are beasts, but otherwise there aren't workhorses likely to pitch so many innings that you'd notice. There does seem to be some thought that great pitchers like these shouldn't throw fewer innings ... but they're not likely to throw more, either. And the non-aces -- the guys who might occasionally luck into an 18-win season -- aren't going to throw more innings, either. Not with the proliferation of seven- (and eight!-)man pitching staffs.
As we've seen this season, 20-game winners are far from extinct. I'm not even sure they're endangered. But they're not coming back like grizzly bears in Montana, either.