The point of a single is to gain radio airplay and thus promote. Miracle Drug would be a spectacular failure for this purpose. Very weak and overall boring song. Virtually nothing says "U2 have hit the wall" like Miracle Drug. I'd say the new song will be out as a single just before this leg of the tour starts, which is a week or so before the Best Of comes out. Which I guess means we'll be hearing the new song in a couple of weeks at the most.