One of the reasons - and fans on other boards are speculating about that as well - might indeed be Adam's marriage. Maybe they didn't want to get promotional work for the album in the way of that event. It is, without doubt, a very important personal event in Adam's life and he might want to fully concentrate on it and on a following honeymoon. So maybe they decided to put everything off a bit because of that
On the other hand the whole "delay" might also happen because U2 have grown apart and hate each other. They only occasionally meet in a recording studio because they have contractual obligations. Now they just don't want to be on a stage with each other ever again. Might be a little problem with an album coming up, promo performances, a possible tour. So they are delaying and delaying and sending Bono off to do obscure radio interviews to cover up the fact that U2 is, indeed, f***ed.
Chose the better theory. In all seriousness, both are discussed in the fan community.