There will be high band but also low band,
this article says t-mobile is already working on it operating in the 600mhz:
http://www.telecompetitor.com/t-mobile-5g-plans-dissent-from-rivals-understanding-mobile-5g-at-600-mhz/and higher frequencies for faster speeds in as many places as they can install it.
Importantly, both AT&T and Verizon plan to use high-band spectrum for the fixed launches, which – in theory at least — should enable them to deliver more bits per hertz in comparison with what T-Mobile can achieve in the 600 MHz band. And that raises an interesting question: Which is the better evolutionary path to 5G – offering fixed service in frequencies capable of supporting higher bandwidth and then migrating to mobile service or, instead, offering mobile service in frequency bands that don’t support the highest bandwidth and then migrating to frequencies that do?
The industry will be watching closely for the answer as all three carriers move ahead with their 5G plans.