And how soon till they set there sights on the 500MHz range?
When over-the-air broadcast television is no longer seen as a need for the public. That'll only happen when there is an equally ubiquitous and relatively low-cost replacement available.
But actually, this upcoming auction and repack
will turn the majority of the 500MHz into solid DTV occupied spectrum. In some areas, this is effectively going to be the loss of both the 600MHz and 500MHz for wireless mics at once. The vast majority of the 600MHz will be sold off the 500Mhz will be filled with DTV stations of every power level, some useable and many unusable.