Gnorog on the EU forums posted notice a while ago that Season 4 is over. That means that all arena teams and ratings have been cleared, and arena charter NPCs have been disabled.
Your arena points will stay with you until you reach level 71 however.
But the end of Season 4 isn't the news.
Season 5 will begin on December 17th for those players that have reached level 80. That's just a few days away. For those that haven't, the skirmish brackets of 71-75 and 76-80 are available. The time is now to start organizing your arena teams and get them in gear for the upcoming events.
With all the changes in Wrath the next arena season promises to be interesting. Here's to bigger and better weapons! /cheers