Season of Discovery Phase 4 launched on July 11, and players were able to finally level to 60 and take on classic raids such as Onyxia's Lair, Molten Core, and the World Bosses of Azeroth. It's been almost a month, and now we're seeing possible updates on the horizon again — patch 1.15.4 is now on the encrypted vendor servers, which could be Season of Discovery Phase 5!
We don't currently know much about what Phase 5 will bring us, but we can speculate — it's highly likely that we'll see the release of Blackwing Lair, and it's a near certainty that we'll get new Runes as well.