Blizzard has posted a preview of the warlock tier 13 armor. You can check it out the whole preview on their blog
Below is the tier 13 armor.
“A set with the flavor of the Old Gods about it – General Vezax from the Ulduar raid was a reference point. Any warlock tier is a great opportunity to bring a dark and warped aesthetic to player gear and this set was especially ripe for the treatment. Replacing the caster’s face with writhing tentacles was the ‘hook’ I started the concept with and built out from there. We always try to include numerous points of illumination into a tier set as it helps to tie the various armour pieces together – whether that be glowing gemstones, fiery runes or, as in this case, bulging otherworldly eyes!”
Based on the info provided, it looks like the tokens for this armor are going to be dropping off Deathwing and his minions.
Blizzard’s preview also has pictures of all the previous tier sets for use in Transmogrification.