Crygil has announced some Arena rating system and requirement changes on the official forums. An in-game update will be improving the rating system of the 3v3 and 5v5 brackets to make it so a similar number of players will be able to have comparable ratings to those in the 2v2 bracket. Also, the personal and team rating requirements for the item level 239 weapons will increase from 2200 to 2350. Here's Blizzard's reasoning behind the change:

"As a result of the above improvements, this change will prevent an excessive number of players from reaching much higher ratings and acquiring the highest grade of weapons in-game. The increase in rating requirements is designed to keep the number of players able to obtain these arena weapons on par with the number of players who are able to obtain the same grade of weapons from Heroic Ulduar."

Once season 7 begins, Blizzard intends to bring the highest rated season 7 weapons back to 2200 and keep the difficulty of the brackets on par with each other.