If the tour is late this year (fall) then I'd expect the release sometime in the summer, to give the songs a chance to sink in before they go out on the road again; not to mention a chance to properly rehearse the new material without it interfering with album promotion.
The final nail on the coffin with Songs of Innocence was the bike crash, thus zero promotion in the US. I think they would want to ensure that's avoided this time around, and let the promos happen prior to the tour and tickets going on sale.
So yea... If a new album is coming this year, I would actually think sooner rather than later. Perhaps June, with a single in May.
Further along it gets, less likely I think it is they release an album in 2016.
This is what I'm thinking. They'll probably want the songs to have room to breathe: promoting the album in all the ways SoI missed out on, minus the bad press of the forced Apple release, plus ensuring the audience at their next shows are familiar with (and hopefully enjoy) the new material.
I'm sure they're keen to avoid a repeat of 360, where the Nloth songs largely fell flat (I remember bono lamenting, "every night we go out and open with a song no-one knows", referring to breathe).
Plus on top of that, as Dan says, they'll need to practice them live; I'm sure they wouldn't want them to be rusty, especially if they're at the forefront of the setlist.
All of that points to the album actually coming out sooner than I'd dared hope (that is, if it does come out).
Of course, option B is that they want some kind of 'casual', or low key release. Maybe SoE will be a smaller album, or they won't care about having it make a big 'splash' like SoI, or it won't be at the forefront of the setlist, instead accompanying SoI material in a chronological style.
... All of that assumes u2 not wanting to be massive, and not wanting a massive album. So yeah, that's unlikely.
What I do fear is a third option: that they delay touring plans (as they already did for early this year), due to delaying SoE, or, worst case scenario (imo), simply push forward with the tour without completing the album, essentially guaranteeing it is never released.
However, if they are truly on track for an album/tour later this year, we could be getting the album in as little as 3-4 months from now. Holy shit!
