Actually this is purely a server update to my knowledge as FFXI is also under going maintenance during this time.

FFXI's notice:
http://www.playonline.com/ff11us/pol...ews20933.shtml

FFXIV's notice:
http://lodestone.finalfantasyxiv.com...2eca224de6ed8b

So yeah, just some server updates (maybe they will sneak the summer event in there as well? I do know--if you don't play/follow XI's information--that they are dropping the PlayOnline servers and making everyone switch over to Square-Enix Account systems so this could be the reason why both the games are going down for the same exact time period)

Case solved? Mayhaps.