The opening announcement in-game tells us that there will be maintenance tomorrow from 3:00 a.m. PDT / 6:00 a.m. EDT until 11:00 a.m. PDT / 2:00 p.m. EDT. Hopefully this downtime won't be a repeat of the patch 3.1 downtime we saw last week where the servers were offline for most of the day and evening.
There is a lot of recent announcements about events happening in the game in the near future. There will be a talent reset accompanying a client-side patch soon, a long list of in-game fixes, and the likely start of season six.
If there is a patch tomorrow, we'll keep you updated on the site with the latest.