I guarantee you this song will be played. Every U2 single has been played, including those released between albums - the least played single is Another Day, but we have only four setlists from before the Boy Tour, so it's certain it was played more than just the two times of which we know. Also, The Swetest Thing, the single from the first Best Of, was played live, so that sets the precedent for the second Best Of's single to be played live. They'd be pretty silly to record a new song, release it as a single, and then just totally abandon it.