There is no suggestion that all of n77 will be used for cellular. That is very unlikely for the foreseeable future.
In Europe only the the n78 sub band is to be used, with an upper limit of 3.8 GHz.
The problem in the US is that FCC has defined an upper limit just below 4.0 GHz, much closer to the air radar band. However they seem to be restricting initial assignments to below 3.8 GHz , which is a sensible move.