Hoping for 2017 although almost no one expected this before 2020 and "5G." CEO Lowell McAdams told analysts Verizon plans "Staying ~two years ahead of competitors in network performance." Massive MIMO and beamforming deliver "Huge gains in spectral efficiency." Delivered wireless can increase two to ten times over the next few years using arrays of thirty-five to hundreds of antennas. A 10x jump wouldn't surprise any of the researchers. Pulling that far ahead is probably an impossible dream. AT&T has almost caught up with Verizon.
Until this week, almost everyone thought substantial Massive MIMO deployment unlikely until 2020 and 5G. The excellent Bernstein analyst Paul de Sa was the first to report "VZ will soon begin market trials of 5G capabilities including 'massive MIMO' (which is when a large number of antennas are packed into a single device) and beam forming (which is when a wireless signal is concentrated on a specific location)." I confirmed with a second analyst what was said.
Beginning trials soon would suggest deployment in 2017 if they go well.