The reason the new album isn't coming out until fall 2013 is because LiveNation doesn't want them to tour until 2014. Let some other mega tours play in 2012-13 (Madonna, Stones, Bruce, Coldplay). Then U2 can be the only show in town in 2014-15.
By 2014, international demand will have rebuilt itself for another massive U2 tour. Honestly, there's no point in U2 putting out a new record unless it's a jumping point for a tour. The amount of money they make off record sales is incredibly insignificant compared to what they make for playing live. Unfortunately, U2 is a business at this point, and that is the smart business model they and their companies will choose.
I think U2 probably has 2, maybe 3 massive world tours left in them. One in 2014-15, and then one towards the end of this decade. There is a possibility that they will do another one in the mid 2020s, if they're all still healthy in their mid 60s. If that be the case, we're looking at 2-3 more U2 albums left. And then after they retire, hopefully they open the vaults!!!