According to an article in DSLReports, the Wall Street Journal report that the FCC was planning on swiping more TV spectrum was wrong. According to the article the plan all along was for voluntary return of spectrum.
I'm not sure if sell is really the right word, but it doesn't really matter. TV stations are bought and sold all the time. However, even if you wanted to limit the discussion to a transfer of spectrum to a different type of broadcast (TV to wireless cell phone like devices) that's been done before too. Qualcomm got a national license for the frequencies of TV channel 55 for their MediaFLO service. The problem was that they had to wait until the DTV transition for those broadcasters who were already there to move out. What they did (with the FCC's blessing) was to offer broadcasters who were sitting on Ch 55 money to move out early so Qualcomm could get going sooner. One example I know of was WLNY Riverhead NY and you can read the request here: www.fcc.gov/mb/video/files/wlny.pdf
But. like I said in the park analogy, selling a station to another broadcaster doesn't take the channel out of the broadcast inventory. It can still be used for TV or radio by a subsequent buyer. The FCC proposes letting the current occupant sell it off permanently.