Ive been told (have not verified) that 900mhz licensee's have until the end of 2024 to find other frequencies..
edit- found an FCC doc that explains a bit..
Location of the Broadband and Narrowband Segments. We designate the 897.5-
900.5/936.5-939.5 MHz band as the new 900 MHz broadband segment and reserve two narrowband
segments—896-897.5/935-936.5 MHz and 900.5-901/939.5-940 MHz—on either side of the broadband
segment. This will result in one paired three megahertz broadband segment that is compliant with 3GPP
standards and two narrowband segments consisting of a paired 1.5 megahertz block and a paired .5
megahertz block, respectively. The NPRM proposed placing the 3/3 megahertz broadband segment at
897.5125/936.5125 MHz (channel 121) to 900.5/939.5 MHz (channel 360).121 However, to comply with
3GPP standards requiring all LTE carriers to conform to a carrier center in integer multiples of 100
kHz,122 we adjust the placement of the broadband segment to begin at the center frequency for existing
channel 120 (897.5/936.5 MHz) and end at the center frequency for existing channel 360 (900.5/939.5
MHz).123 The placement of the broadband segment so that it conforms to 3GPP specifications will
encourage full use of the band and increase equipment availability.
https://docs.fcc.gov/public/attachments ... 3915A1.pdf