Only Massive MIMO in TDD spectrum has gone beyond testing but China Telecom, Sprint, Huawei, and ZTE are confident commercial FDD products are close. Their press releases about FDD tests are enthusiastic. However, systems based on TDD (Time-division duplexing,) are deploying by the hundreds and soon by the thousands, but FDD (Frequency-Division duplexing) systems are just in early testing. The choice between FDD and TDD is driven by spectrum availability. The majority of spectrum in use is FDD.
Massive MIMO requires constantly updated Customer State Information (CSI.) The cell needs constantly updated receiver location and capability to steer the many antennas. The overhead is considerable, possibly too high to use FDD in many places. FDD systems appear to have lower capacity but there is almost no data from the field.