From what I've heard srcset is the likely eventual standard (as oppose to the picture element) but the timeline there is...long and murky.
Unfortunately the browser vendors get to make this up as they go along and they seem unwilling to take into consideration the many developers which are more in favor of the <picture> element because its so much easier to write.
Naturally, if/whenever it is implemented we'll all scuttle back to our keyboards and play with srcset .