The reason for that are major changes to the movie, like turning it from one into two, and Hollywood sitting on their hands. Don't forget the anime!
The new Mad Max flick stars actor Tom Hardy and he reveals that the studio powers that be have "pushed it back a little", which means stars and crew have looked elsewhere to keep them busy during this schedule chaos.
The film and game are linked in soul, if you will, meaning the film crew are chatting with the game developers to make sure they're all on the same narrative page. This also includes the work behind the in-development anime too.
Until Hollywood gets their sh*t together, expect more eerie silence from Mad Max.