Blizzard mentioned (yesterday):
“We’ll be performing maintenance on our authentication systems this Tuesday, June 8 from 11:00 PM PDT until approximately 2:00 AM PDT. During this maintenance period the ability to log in may be affected. If you’re unable to log in to the game or online services during this maintenance period, please try again once it has concluded.”
There is no confirmation of what’s really going on. According to some people, world of warcraft servers will be down for at-least 24 hours in the United States because of maintenance but that doesn’t look like the case.
According to relam status (WoW Utility), most of the servers are up. So In my opinion, all the rest of the servers will be up soon.