If standing desks ever take off, I wonder if we'll eventually face news articles with titles like: "Standing for hours can shave years off life"...
Very, very unlikely.
The whole "exercise good, sitting kills you" thing was first noticed in England among bus drivers in 1953. There the driver and conductor were from similar socio-economic backgrounds, similar pay, etc, but one sat all day, and the other stood. Drivers died much faster than conductors. Every significant followup since has confirmed the basic conclusion. Sitting all day is not healthy for us.
From Wikipedia, "[...] sedentary drivers of London's double-decker buses had higher rates of cardiovascular disease than the conductors who climbed the stairs" and "[Jerry Morris] performed further studies that showed slow movements such as gardening helped very little and exercise had to be more vigorous to help."