Remember awhile back when there was a post mentioning that Blizzard had no implications to do maintenance on tuesday?
I was just reminded that there are several key features that have not been implemented yet such as old world flying and guild leveling/guild features/perks - Think it will just arrive in a short update? Because if it does - i suspect there will of course be tons of issues and they will have to apply hotfixes, I would not be surprised if there was some moderate downtime for quick rolling restarts following the release.