I am fascinated by Cataclysm, the upcoming WoW expansion, because it represents a very different sort of expansion. Most MMO expansions change the world by adding new content to the edges of the world. Sure, some of that new content may be for low levels (especially new races), some may be meant to fill in holes in the middle levels, but the majority of it is usually intended for the upper levels. That division helps separate the old and new content in very obvious ways.

But Cataclysm will be restructuring the oldest part of WoW enormously. That clean division of old and new content … not so clean anymore.  Now I’m an old hand at MMOs, but I’m not entirely sure what to expect from this one. And that goes double for how and where new pet families may be introduced.

Pet families have never been explicitly limited by expansion — only by the level and location. For example, moths and wasps were added in Wrath of the Lich King but can be tamed by a hunter with only the Burning Crusade because they occur in Outland.

Chimaeras and silithids, on the other hand, can be tamed by any level 60 hunter, whether they have any expansions or not, because they occur in old Azeroth. (True, you need Beast Mastery to tame them, but talents are available to all hunters, and you can get Beast Mastery at level 60 if you plan carefully.)

How is this going to work when the old and new content are so thoroughly intermingled? Gilneas and the goblin starter area will probably be set off, much like the Draenei islands and the blood elf area, but it sounds like the majority of changes will happen in commonly accessible areas. Does this mean that if we get new pet families, they will be largely available to all hunters? Or will we see new families only in the explicit expansion areas?

Let’s take a look at the history so far. When it launched, WoW included 17 pet families:

1. Bats
2. Bears
3. Boars
4. Carrion Birds
5. Cats
6. Crabs
7. Crocolisks
8. Gorillas
9. Hyenas
10. Owls (now Birds of Prey)
11. Raptors
12. Scorpids
13. Spiders
14. Tallstriders
15. Turtles
16. Wind Serpents
17. Wolves

Patch 2.0 and the Burning Crusade expansion added 6 pet families — an increase of about 35% — for a total of 23:

1. Dragonhawks
2. Nether Rays
3. Ravagers
4. Serpents
5. Sporebats
6. Warp Stalkers

Patch 3.0 and the Wrath of the Lich King expansion added 9 more — an increase of about 39% — for our current total of 32 pet families:

1. Chimaeras
2. Core Hounds
3. Devilsaurs
4. Moths
5. Rhinos
6. Silithids
7. Spirit Beasts
8. Wasps
9. Worms

On a purely historical basis, we might expect another 10-12 pet families (an increase of about 31%-38%) from Patch 4.0/Cataclysm. Or we might get no new pet families at all …

At this point we really have no idea how Blizzard will draw the line between Patch 4.0 content — available to everyone — and Cataclysm expansion content proper. And that means that we don’t really know how the new pet families — if there are any — will be available and at what levels.