WebKit has implemented srcset and I can’t help but feel this is a step backward and a band aid solution. There are many thoughts that come to me when I think of the short and long-term effect something like this can have on web development.
I’m sure hi-res graphics have their place in certain circumstances, but having an additional property on an html entity seems heavy-handed and a bit backward in thinking. We have media queries in CSS, why isn’t targeting devices that have the screen resolution and internet bandwidth to take advantage of hi-res graphics part of the media query process? HTML, in my opinion, provides the bones in which you build everything off of. You don’t make a <hires> tag when you want to show something hi-res.
Frankly, the <img> tag is a legacy entity that has really lost it’s power since the advent of CSS and the <div>.