Take a lesson from the user backlash that happens every time a browser removes a feature: Don't do that. The best you can do is encourage developers to use an alternative. The worst you can do is to force it on people who don't share your point of view.
He isn't saying that browsers should remove the "Save as..."-feature. However, he is suggesting that browsers and websites should implement the download-attribute, which he believes will make the need for "Save as..." go away in those cases.
