And the other things is, it really doesn't matter if Adam was joking or not, as the band members don't really know how long a record will take to record until they have the songs in place. I remember Adam talking about starting to record Bomb, saying with 6 leftovers from ATYCLB, they could get a project together....and then when they did get another 6 tracks recorded, by all logic they should have had the album out....but alas, it wasn't until another 3 years after Adam's statement...so you just never know.
That said, if U2 has the leftovers they say they do from the Bomb sessions, songs such as 'North Star', 'Lead Me in the Way I Should Go', 'Mercy', 'Love is all We Have Left', and others, along with the tracks they demoed and wrote this summer - and the fact that it is Rubin who is producing - I don't see why it should take that many working months to complete and album. But that's the key - working months. They just have to make the time around the tour and holidays. If they do, I can see an album out by next year - maybe even a summer or fall release. But that all depends on many things, not just time constrainsts, but also production team (do they bring back Rubin after the tour is over? What's his schedule like? If Lanois and Eno come back, give the album another 3 years!)...also things like the direction the album takes. What kind of production do the songs demand? What kind of work do they need? The songs will dictate so much of the equation.
In short, this album could be finished in 6 months or 2 years. I don't see it being finished in 2 months. But U2 has surprised me before...so there's always hope for the unexpected.