I may be wrong here, but i doubt the version we've heard is the one that will be officially released.
Firstly, if EBW is indeed the first single (or even second, third, etc), u2 probably want the song to sound fresh when it's released - as in, have a version that no one has heard before, and will want to buy. If they play a full version now, everyone will have heard it months before its release, and it would probably flop as a single. Playing an acoustic version is like a teaser!
Secondly, the band seem to want to play a gentle, acoustic song at that point in their set list, accompanied by ISHFWILF, then in a little while. So maybe they think a full out, rocking version of EBW would disrupt that portion of the setlist?
But yeah, i think the first point would explain why we're only hearing a stripped down version.