I think that's a logical place to go if they intend to give a new pet. Although I'd love to control one of the four-armed ladies from TBC (The problem is they would probably be a melee dps pet which warlocks already have more than enough of...but it would look cool!)

As for the dev quote...sadly I didn't interpret the comment as a hint of a new pet per se. That could be, but my first thought was that he was referring to new abilities for existing pets. /shrug

THIS!!! ^^

The Shivarra (the four-armed ladies to which you were referring) would be an AWESOME choice.
Although I'd see it more as a melee buffer, as opposed to a melee debuffer that the succubus is.

I want to see more pet choice aswell, with pets doing similar dps and choosing one for utility rather than just a static "Use this pet coz of the dps yo".

Eg. Destro locks have the choice between an Imp or Shivarra, with the Imp buffing with health as it does now, while the Shivarra buffs with a Judgement of light/Healing stream totem esque ability.

Affliction locks choose between a Felhunter (new model plz -_-) and a Succubus, with the Felhunter good a locking down casters with interrupts, silences and magic damage reducing debuffs, and the Succubus good at locking down melee with disarms, reducing attack speed/dmg done etc.

And next demo locks.
Demo should always have the Felguard out (Or be able to upgrade it to a Wrath guard) as it is the iconic demo pet, but they should also be able to bring out a Beholder for extra dps and a replenishment buff or something every 2-3mins for 1min, similar to dk ghouls.
Eg. you will always have a Felguard out, but you will have a Beholder every 2-3 mins as a dps CD that lasts one min, and they could have some extra buff that only lasts a little while, like replenishment or a weak MS.

And finally, temp pets.
Infernal should be more of an AotD type ability, a wipe saver in a 5man or raid, with extremely high health and amour with taunts and good damage spells, but only last a little while with a long (8-10min) CD.

Doomguard should be (IMO) a situational pet, a high risk, high dps type typer pet that requires a ritual to summon.
Curse of doom should be done away with tbh.
And after performing the ritual it empowers your demon to be far and away more dps than your standard pet (minus the buffs though) with unique abilitys and the Doomguard model ofc.
But Doomguard buff has to be refreshed (by simply re-clicking the ritual ability) and the longer your demon stays in that form, the more likely it is to wreak havoc on the raid and break free.
Maybe have it last at least one min (refresh it every 30secs) with no chance of it breaking free, and after that ever time you refresh it has a higher and higher chance of breaking free of your control.

Just my personal idea (WISH!!) for Cataclysm demons.
Peace out :D

I disagree. I think they're going to make infernals function a bit more like they do in the Jaraxxus fight. They'll be temporary guardians that, instead of replacing the pet, function autonomously to provide a temporary dps boost and threat manipulator, like Army of the Dead.