There is a new system on the line in Patch 7.2: Pet Battle Challenge. You will get rich rewards to complete Pet Battle Challenge storylines and challenge quest. 
Pet Battle Challenge is similar to the 5-man dungeon. Player arrange their own battle pets to defeat the monsters or bosses from the dungeon. 
The player can obtain the quest in the broken islands of the Dalaran pet trainers. With the quest of the storylines, you will reach Wailing Caverns, then you can enter the dungeon. 
The first time to enter the dungeon only needs a level 25 pet. Of course, then more you have the pets, the easier you get clearance.
when you complete the dungeon first time, you will get a piece of ultimate fighting training stone. Then you can start the dungeon challenge.
You can do challenge quest once a week. After the Challenge dungeon is open, you can't heal and resurrects your pets. In order to complete the Challenge, you need enough level 25 pets. 
You will get the achievement and Damp Pet Supplies after Completing pet Challenge dungeon. Damp Pet Supplies have a chance to get 3 new BOE pets: 
Cavern Moccasin
Young Venomfang
Everliving Spore
Of course, you can purchase these pets by WoW Gold from the Auction House.
As well as the upcoming Pet Battle Challenge: Deadmines, I believe that it will be more and more exciting for pet battle in future.