South Korean MNOs agreed to launch 5G at the same time
In a Press Release dated July 2018, the MSIT announced that the three South Korean MNOs agreed on a jointly 5G launch in March 2019. Let us bear in mind that the three South Korean MNOs agreed to share 5G deployment and network earlier in April 2018.
The intention aims at avoiding a very costly launch campaign when 4G came to reality back in 2011 and generating heavy cost savings of nearly 1 trillion KRW over the next ten years according to rcrwireless, see here).
This announcement also follows 5G spectrum auctions of 3.5 and 28 GHz spectrum in June 2018.