I got a chance to see the map the Office of Planning put together for the SmartBike expansion. They broke them out into Round 2 and Round 3 expansions but since only 28 of the 40 kiosks are shown I think all of them will be done this summer with the $3M in stimulus money. Here is what I got from it. I should note that it is not official or complete.
There will be kiosks all over the District, from the Capitol Heights Metro on the eastern edge to Friendship Heights on the west, and from Takoma Metro to Congress Heights. As you may have figured out, most of the kiosks appear tied to Metro stations. Some exceptions include Adams Morgan, Mount Pleasant, Georgetown and H Street. [Update: I had these last two sentences reversed, changing the meaning.]
Some of the distances seem long and there aren't any shown on the Mall or in Arlington on the other side of the Key Bridge, but like I said there are 12 more that weren't on it and some of these (especially Takoma - for which the next nearest kiosk is in Petworth) may not happen.
It appears OPM used a combination of employment density, population density, shopping density and bike to work rates from the 2000 census to define the new locations.