There is definitely something going on in recent months though. This Norah Jones article only confirms it. I cant help but feeling that with the band being away recently ( e.g Bono's been in Israel and Peru) , they are perhaps keeping the summer free to wrap up the album. The activity around HQ recently could point to that. If we look at the fact that they have been in studio during 360 and with Adam even saying they did not want to go away for years again , maybe its a possibility after all.... 
Yeah that's a good point. Bono seems to have been all around the world the past few months, which makes me think nothing serious is happening. But then again, there having been sightings of the band, their technicians and their equipment around studios, plus articles about them working on a new album. And I think Bono still travelled during the making of NLOTH.
Maybe they're just casually working right now, and as you say, will focus more in the late summer. Or perhaps they've done most of the work, and all the sightings are just them putting finishing touches to the songs.
I'm really not sure - i think it's been way too soon for them to have finished an album (i'm trying not to be optimistic). I think they probably came close to releasing an album in 2011, during the tour, so they could've had quite a lot finished already, but Bono's most recent comments were about all that 'three albums' nonsense (which sounds suspiciously like 'getting lost in the music' - aka nothing's really concrete yet - to me).
Then again, they have been very quiet since what... january? And we know they have been working. It's possible that almost doing a mid-tour album gave them a massive head start, and something's coming soon... but it's just as likely that they've started from scratch, and no serious progress has been made, even if they have been in the studio.
To avoid disappointment, i'm gonna assume the next few comments we'll get from them for the rest of 2012 will be vague "getting lost in the music" type lines.