In reply to John Teague.

This is not about prolonging support for IE8 and IE9, but about providing a great user experience for those still stuck using older browsers while still implementing new technologies. Unlike other advancements like media queries, responsive images, and so on, flexbox has not had a proper polyfill that allowed us to use it in production. Now we have it thanks to 10up, and as far as I'm concerned, Flexbox is now ready for production.