Here's an interview with Miroslaw Przedpelski, member of FIVB and ex-president of polish federation (unfortunately only for those who speak Polish):
http://www.sport.pl/siatkowka/7,64948,24066894,siatkowka-miroslaw-przedpelski-turniej-kwalifikacyjny-do-igrzysk.html
Few things about olympic qualifications:
- world ranking will be published January 1st 2019 and its rules will be established in November during congress in Mexico
- probably points for ranking will be count from World Cup 2015, World Championships 2018, Olympics 2016 and qualifications for last two (there are other ideas but Przedpelski says they will not pass) so it's possible that neither World League 2017 nor Nations League 2018 will count
- six intercontinental tournaments are 100% sure (nothing new but it's FIVB so it is worth mentioning, I guess)
Moreover he says why World Cup 2019 isn't olympic qualification anymore. The reason is that it's held in Japan and FIVB members was afraid that after the tournament there will be opinions that Japanese forgive some matches because it will be only friendly tournament for them