after some research and calculations, short answer: YES!
longer answer:
this comes to a total of 114 in-game pets currently available. this excludes all special events pets (such as blizzcon, the 2008 olympics, etc.), companions that are not available in the USA, and pets bought with RL money.
- 49 vendor pets - these can be purchased from an NPC using some form of currency (such as gold, champion's seals, etc.)
- 36 dropped pets - these are companions that require some farming
- 16 quest reward pets - pets rewarded at the end of a quest chain (excluding either the argent gruntling or the argent squire since you can have only one, not both on the same character)
- 5 crafted pets - this is including the pet bombling and lil' smoky since they will no longer be bop next patch
- 5 pets earned through achievements - this does not include achievements of past that are no longer obtainable (such as WoW's 4th anniversary)
- 2 pets obtained through either a vendor or can be dropped from a mob or other form of spoils
- 1 pet obtained through either a quest or can be dropped from a mob or other form of spoils
so what does this mean?
this means that nearly any WoW player with enough patience, determination, time, and sometimes gold can indeed reach the current highest level pet achievement tier (lil game hunter). the achievement requires the player to collect only 75 pets, and as you can see, with many a combination of pet collecting, be it gathering only the vendored pets plus the ones that drop off of creatures or collecting the quest rewards, crafted, vendored and just a few world drops, almost anyone can complete this achievement. this is all without spending real world money, attending special events either IRL or in game, or participating in limited time offers.
in light of this, and with the growing number of potential pets just over the horizon, it's high time for a 100 vanity pet achievement. or even 125 if blizzard is feeling extra devious (this would be significantly harder for people to reach since there are only 114 companions readily available atm).
with more and more readily available pets being introduced onto live servers, it just doesn't make sense to leave the cap for noncombat pet collecting achievements at 75. it's a relatively easy number to reach, therefore not much of an "achievement" lately.
blizzard has to have something up their sleeves. i'm itching for a challenge or at the very least a new goal to aspire to. something that will take some time, some effort, but be very rewarding. in other words the definition of "achieving" something special?