"The last time the FCC opened up some spectrum, we got WiFi."

That's rewriting history somewhat. The Industrial/Scientific/Medical (ISM) unlicensed bands including 2.4 GHz were allocated by the FCC in 1985. The IEEE 802.11 standards which are the basis for WiFi weren't finalized until 1999, which is 14 years later. So it's not quite true that WiFi rushed to fill some newly opened spectrum. The ISM bands were around for a long time and used for many other purposes before WiFi came along.