According to the BBC's David Ornstein, Arsenal will name defender Thomas Vermaelen as team captain for the 2012-2013 Premier League season. Vermaelen was the vice-captain last season to striker Robin van Persie, who will (most likely) be playing for Manchester United this season. This, of course, would represent a conflict of interest if he were to remain Arsenal captain.
The club will likely announce this in the next day or so, and soon after we will have to endure a week (or year) of jokes about Vermaelen leaving to Barcelona or United or something. So it goes.
Vermaelen had a bit of a hit-or-miss season on the field last year, but his leadership has never been questioned, to my knowledge. There were a few other options that were bandied about - some floated Mikel Arteta or Bacary Sagna as possible captains - but Vermaelen was always the most likely.
I'm hopeful that the armband will instill a sense of honor and duty in Vermaelen even greater than before, and that perhaps that will make him occasionally stay back near the goal and play some damn defense occasionally.