It looks like the days of adding attribute filters and body attributes to styles in media queries just to address the Yahoo! Mail media query bug are finally over.

No more attribute selector syntax in media queries!

@media (...) {

Not only does it appear that they've fixed the bug, it seems they're supporting responsive emails (min-width, max-width). There's also the possibility of a new Yahoo! Mail client targetting technique leveraging a quirk in how Yahoo! Mail processes media query declarations.