If it took Corbijn and U2 until the end of January to take, decide and finalize the CD artwork, they could give it to the label, with the mastered album and it could be out by April or maybe May.
Then again, if Corbijn updated his webpage in 2 weeks and said "we are still working on the U2 artwork" there would be people on this board saying that the album won't come out until fall.
People don't think the band is 100% done with the album, they think the band is done recording the album because Bono and Adam said it was finished a few weeks ago. It was mentioned in at least 3 seperate articles, and it was reported firsthand on the PLEBA forum, check it out for yourself.
The HARDEST part of the process is recording the material. Apparently, they are done with that part.
How complicated do you think taking photos is? It could be accomplished in a matter of hours, or at the most a week. Considering they probably already have some to work with (from London) then it could take them just as long to deal with the artwork as it does for the engineers to mix and master the album.
In fact, artwork is the most simple of the remaining processes that stand between us fans and an actual announcement of a release date.
Look at it this way. In order for Corbijn to begin work on the artwork (as he's stated on more than one occasion) he has to know a theme and prospects for what the album might be titled or else he wouldn't know what to shoot. This is the first clue that the band were done or nearly done, when they first shot in London. All this means is that they didn't like how it turned out.
They had to have known the theme for the ATYCLB shoots when they went to France to shoot in the airport.
I'll do some homework and see if I can find when U2 and Anton Corbijn went to France to shoot in 2000 and look at the realtionship between that time period and when the album and singles came out in 2000. If memory serves me they did it in July 2000, but I will verify.
It might be April, or maybe May (doubtful) instead of March. But that's that big of a deal when we've been waiting this long.