According to Blizzard:
[I]n this case, the Scorchling will return elsewhere along with some friends representing the remaining elements.
So rejoice, pet collectors! The Scorchling will be back!
The Good: NEW Pet!
This year, killing Lord Ahune grants players access to an all-new companion, the Frigid Frostling! Farming for this pet will be a little different than past seasonal farming.
For starters, it's now much easier for players to access seasonal bosses. Via the Dungeon Finder tool, players can select the seasonal boss and instantly teleport to that boss' dungeon. The first time the boss is defeated each day, it drops a special bag (very similar to the way a Random Heroic Dungeons award Emblems of Frost). This bag has a chance to drop the rare boss loot, such as companions and mounts.
Early reports indicate that the drop chance for our new friend is approximately 1 in 20 (about 5%).
The Bad: Bye Bye Scorchling
It appears as though the Scorchling pet that so many of us were waiting to farm has been pulled from Ahune's loot tables. While a small number of players claim to have seen this pet continue to drop, Blizzard says otherwise:
I'm afraid that the Scorchling does not appear to be available this year, folks. I cannot say for certain whether or not it will be made available in the future; however, we encourage you to share your thoughts on the Suggestions forum if you would like to see the Scorched Stone be obtainable in some other way.
We remain hopeful that the Scorchling, much like the Spirit of Summer, will become available by some other means in the future.
A special thanks to the folks at MMO-Champion for helping us with the Frigid Frostling's picture. You guys rock!