Too Soon, He Says

Looks like we all got excited a bit too soon. Zarhym made an official post about Pet Battles on the beta:

"While we've received a number of questions and some feedback regarding the pet battle system added in the last beta patch, we're in the process of disabling this feature. We know a lot of you are very anxious to test out pet battles, but it wasn't our intention to introduce them to the beta at this stage, as we don't yet feel they're in a solid enough state to allow for meaningful feedback.

One we're further along in development, we look forward to implementing pet battles and gathering your thoughts on the feature." - source

Sadness! But it was definitely interesting and fun while it lasted, and this teaser preview makes me even more excited and eager to see a more finalized version of this new feature.