President of ArenaNet Mike O’brien posted an updated on the GW2 forums that this episode will take the 3 month cadence instead of the 2-3 month cadence they have being doing.
"We’re currently putting the finishing touches on episode five. It’s an important episode and we’re taking the time to get it right. I wanted to let you know that this episode will release closer to the three-month side of our two-to-three-month cadence. We’ll make the formal announcement when everything’s locked down. In the meantime, just hang tight a little while longer."
https://forum-en.guildwars2.com/forum/game/gw2/Ep5-update