Take off your tinfoil hats people. There's been a lot of interesting speculation here about Lego manipulating the market with Machiavellian strategies. The Town Hall is retiring because it was the slow seller of the theme and that is that. For it's entire life it sat on the shelf at $200, right next to the beautiful Grand Emporium, the fun Pet Shop, the romantic Parisian Restaurant - all of which were much cheaper, and were more emotionally attractive. Do you want to dream of having your own pet shop one day? ... or dream of having a bureaucratic job at City Hall? It was always peoples' 2nd or 3rd choice, so it didn't sell well. Mystery solved.
I made a list of about 2 dozen "rare" part numbers for the TH (parts used in the TH which were unique, or shared by no more than 2 other sets). I was interested in the "eliminating rare parts" theory ... but even I don't buy it. If the Town Hall was a hot seller, it would still be available today. Eliminating a dozen or so part numbers is a small, small bonus for Lego, but in no way a deciding factor. A similar list of "rare" parts for the Detective's Office would have over 40 part numbers on it - many of which could have been substituted with more common parts... but obviously, the design team wanted "that certain shade of blue", or unique new hair on that minifigure... clearly part number proliferation is not a big concern for Lego.
And resurrecting the Town Hall? That ship has sailed. Lego recognizes this "after death demand" for what it is. If they produced another batch, investors would snap them all up. If they went into full production, and continued to carry this model for another year or two, many investors would be very hesitant to buy more exclusives. They would be shooting themselves in the foot.
Last year, Feb 4th, 2014 was Retirement Apocalypse Day... dozens of sets got their "Retired" tag that day, even though most had been gone for months. I expect TH will earn it's badge within the next few weeks.