2017's biggest announcement - unless China does similar. NTT Docomo CEO Kazuhiro Yoshizawa plans to go "nationwide" by 2023, per the generally reliable Nikkei Asia Review. The estimate is that the three Japanese telcos (DOCOMO, KDDI, Softbank) will spend a total of ~$45B, some of it on shared infrastructure, The story has been picked up by more than a dozen publications but that's about the only details we have. (If DOCOMO is spending half of the $5G, that's about $200/person servable.)
DOCOMO has been dropping hints for several months. I'm hoping for a detailed announcement either at the June 20th shareholders meeting or the next quarterly conference call. Nikkei has a May 22 comment from Yoshiwara "We will lead the world with our 5G technology."