Oy and vey.
Okay, so here's where I am, I came here to look it up, because I too wanted to know what was up with the Spectral Cub. It's listed, I was curious, and so I came to look.
Now, a different thing came up in this thread, and that's the issue of "rarity" and "difficulty" obtaining an item. Take a moment and really think about what you are saying. It's incredibly short sighted and a little bit mean.
You have something, you feel you put work and effort into it, and because of that you want to be "special" and no one else should be allowed to have it. How unfair is that? What if someone started playing WoW TODAY and got into pets only to find out they will NEVER be able to get a spectral cub just because you want to be a special snowflake? And what happens when you quit playing? And the new person still is? Your pets rot on a server somewhere never to be seen again and that new player could end up LEAVING the game because they feel like they can't be a part of something because people decided they wanted to be special and have something no one else could have.
Rarity in WoW is a fallacy. The rarity of an item is determined based on the people you play with, not WoW as a whole. Here's my example: In wrath, when the Sparkle Pony hit the mount store, everyone bought one. Everyone. Two months later, NO ONE was riding one, because they had all moved on to the new flavor of the month mount. But in my little guild of about 15 people, only two of us had the Sparkle Pony. But because of everyone being silly, TEN of us had Baron Rivendare's mount. So when we mounted up as a guild, the Sparkle Pony was much much more rare, due to the fact that no one had one. Things are only rare or common based on the people you play with.
I know people who started playing long after the Vampire Batling in Kara and the Olympic dragons were introduced and removed. One of them LOVES the dragon but can never get one. She will never have one. Despite it being her favorite pet. I don't ever bring mine out because it quite literally bums her out to the point she doesn't want to play.
As far as I am concerned, give it a different name, just like the Cenarian Hatchling, and do it. Give a feat of strength for having the TCG one or something. Put the TCG mounts and pets all up there. Let people buy them and collect them as much as they want. Your epeen is intact because you can point and say well mine is the Spectral Tiger Cub and yours is just the Spectral Cub, so look I am still a mad collector. They get to have a pet they really love and enjoy. Two weeks after the pet hits the store they will have moved on to a new pet and yours is just as rare as it always was.
And before someone says something about me wanting them, I have a spectral tiger cub. I had THREE hippogryph hatchlings before the Cenarian one hit. I have all the TCG pets. My husband paid $1000 to buy me a Spectral Tiger mount card, which I got long before the account wide mounts was even heard of. That doesn't show any "difficulty" or "effort" beyond clicking through eBay. It just shows I have stupid amounts of money to spend on PIXELS. It is just PIXELS. There is no effort involved in getting these pets. There is nothing special about them. There is no reason everyone shouldn't have a fair shot at them now. You have had years with them being your special pet. Now is time to realize it's better that everyone have a chance to have one. It shouldn't be an exclusive club limited only to people who have large amounts of discretionary income. If I had my way, you'd be able to buy every TCG and Collector's Edition pet from the pet store. It would just make life easier and I would get to have every pet I wanted, instead of spending hundreds of dollars that goes to re-sellers on eBay.
Also if you really want to show off effort, then do things like the crawling claw and lil' tarcogosa (sp?). Those take effort, and are still feasibly obtainable by everyone.
TL:DR - Pet collecting shouldn't be an exclusive club limited only to people who have large amounts of discretionary income.