Rob points us to this rumour at U2 Gigs. I quote:
North American tour rumour
And now it’s tour rumour time! Our friends at U2log.com posted some tasty morsels on their Twitter account. They report that the North American tour will be in arenas, which is in accordance with Wednesday’s rumour. The tour will comprise lengthy residencies in seven cities. They will set up camp in a city and play as many shows as they can sell in the same venue; these shows may not be consecutive to take into account Bono’s voice and venue scheduling factors (e.g. NBA and NHL).
Toronto was the only city mentioned specifically. U2log speculate that New York, Chicago, and Los Angeles can probably rest easy. Our speculation is that Boston would be another likely candidate because of U2’s rich history and strong connection to the city. So North American fans, if you live outside the seven selected markets, you may have to prepare to travel.