Ericsson and Verizon is already working on 5G RAN bringup and qualcomm is about to release 5G chipset using dual connectivity.
So maybe by mid of 2019 5G non stand alone RAN architecture will be brought to commercial usage.
3GPP have release 38 series spec for 5G RAN and core network . other vendors are already working on stand alone architecture with NG-Core , so maybe 5G will be coming to commercial use after 2019. My opinion is 5G work is already in progress .