If you missed it, MMO-Champion now has a preview of the Eye of the Legion pet. It was datamined from the patch 4.3.2 PTR. And according to this tweet, this pet will be from the TCG expansion deck Timewalkers: War of the Ancients.
There are still two more TCG sets that need to be released (Crown of the Heavens - scheduled for release some time in February and Tomb of the Forgotten - likely to be released a couple of months after that), so Timewalkers will probably be released sometime late spring/summer.
I'm actually quite excited about the Eye of the Legion pet. We all get to pretend to be warlocks! There are so many awesome possible idle animations for this eye companion, I just hope that the developers have it do something neat other than just hovering about. We'll see.