ATSC 3.0 is not tied to any particular frequencies or channel layouts. Should ATSC 3.0 make a go of it, will be in all US TV bands because there isn't room for both DTV and ATSC in just the upper ranges (unless you live in a very isolated area like Montana, Wyoming or Eastern Oregon). It is possible that stations will move their DTV signals to VHF so they can reserve their UHF bandwidth for ATSC 3.0 but you'll almost certainly need to retain access to the DTV channels at least until you can replace all your tuners. This time around, the gubmint isn't going to sponsor converter boxes and they're telling us that there won't be any hard and fast deadlines for converting over as there were the last time around (NTSC->DTV). However, there will be conditions on adoption of ATSC 3.0 (or whatever next generation modulation standard makes the grade) as the replacement broadcast TV standard for DTV.