As Mania reports, the new Thunderstomp, in the 3rd tier of the tenacity pet tree, does a bit less damage than the highest rank of the current Thunderstomp, but it does still have the attached threat. It should at the least make it much easier for any tenacity pet to tank multiples, and officially lay to rest the title of Gorilladin.
Of course, Gorillas probably won't disappear into the mist either, as their replacement skill is Pummel, a copy of the Warrior skill that interrupts spell casting. Thus in one fell swoop, Gorillas may have just become the preferred Arena pet.
As far as how this will all synergize with current family skills on other pets, I expect Crocolisks and Bears especially to jump to the forefront of tenacity pet popularity. Their multi-target attack abilities will combine with Thunderstomp to create some nice AE threat and DPS, perfect for farming or pet tanking at any level. I don't think the Acid Spit armor reduction of the worm should be taken lightly either, and some Hunters may like the extra defensive power of the Turtle.
But this, combined with Blizzards other moves of equalizing pet stats and adding other new talents and skills to each tree, should make choosing a pet for looks rather than skills a lot less painful for your overall DPS or utility. When the really good stuff is located in the talents, you can finally grab that Crab without regret. This could all change before 3.1 goes live, but here's hoping Blizzard decides to keep these changes. More customization is always more fun.
Patch 3.1 brings us Ulduar, dual specs, significant changes to all the classes, and more! We've got you covered from top to bottom with our Guide to Patch 3.1.