Spooncraft

    It’s not really confirmed when season 4 will begin, but presumably it will be a little after patch 2.4 goes live and people start seeing gear from the new 25 man Sunwell raid. Bornakk pretty plainly says that when season 4 begins, the season 2 “merciless” gear is going to drop off the vendor list and be moved to the honor gear vendors just like season 1 arena gear did when vengeful gladiator items were brought into the game. As pure speculation, the new reputation vendor PVP gear that’s supposed to be obtainable through PVE endeavors might just be the season 1 gear getting its final drop to the bottom of the viability list.

I can only hypothesize that season 4 will begin when the Sunwell is released just based on the item model trends, season 1 gear is a recolor of Tier 4 loot, season 2 is tier 5 and so on. Blizzard has specifically said that there won’t be any token rewards (class specific gear) coming out of the Sunwell but that the armor sets that will be available will be recolored models based on armor class. Like plate sets that are obviously meant for a holy paladin or DPS warrior, they’ll look the same but have different stats, bonuses, and of course coloring. (src)