"If you see this on PTR, don't worry... we'll be adding way more trainers to it."
It would appear that the developers have decided to implement the Elekk Plushie (perhaps as is) and award players who can defeat difficult trainer battles with this pet on the active team with an achievement. This was a pretty popular request by players once news of the plushie pet and its inability to be efficient or useful in battles started to spread. I guess developers liked the idea and decided to run with it!
Personally, I have mixed feelings. I'm up for the challenge but I still can't help but feel bad for a helpless stuffed animal/pet. As a child my toys were never the ones that got beat up, they always won the battles damnit. Even against each other, I made sure they all had a fighting chance... unless I didn't particularly like/enjoy the toy. I adore all my in-game pets, so I just feel guilty and somewhat sad knowing that I'm sending a less than optimal battler into a fight.
Anyway, hopefully the achievement will be interesting to complete and not too much of a pain.
Another tidbit LeCraft mentioned on Twitter is a nod to a fellow pet lover, Eleanor Wroblewski (aka: @undeadgoat on Twitter). This ghostly goat is appropriately named Eleanor and will be a "boss" pet that players can battle against. :D
There are quite a few nods to pet collectors/battlers and ideas from the community that are already popping up in WoD, and it's always nice to see more! Wowhead has a huge list of other community references -- just search for the word "pet" and you'll find many other awesome ideas that originated from pet lovers. :)