Third time? What was the second?
Don't think they would (release it as a single). I guess if they've bothered to properly re-do it like this, it means it's a good chance to appear on there (and I wonder if they've done it for anything else - e.g. they've always said that they felt they never got the Fly quite right on the album - Bullshit! I say - and they, obviously, play it quite differently live, so maybe?), but I would think, and hope, that if they release something it will be something 'new' from that era.
And this is a cool different version for 'us', but I don't think this version comes even close to being as good as the original. And - IMO - that might be something a lot of people would agree with? i.e. releasing it might just run the risk of it just being another point scored for 'U2 ain't what they used to be'.