Kishimoto's habit of revealing new powerful techniques, then to be continued.
Here are the examples:
Itachi's Susanoo
Sasuke's Kirin
Izanami
Madara's Double Meteor
Madara's Perfect Susanoo
Pain's Chibaku Tensei
Konan's Paper Person of God Technique
Kabuto's Sage Art: White Rage Jutsu
etc.