I happened to be browsing the official WoW hunter forums and saw a post that you can now tame a new pet while you have an existing pet active, so long as your active pet is dismissed. So I tried it out, and yes, you can. But the behavior is … odd … and I don’t know whether it’s intended or not.
If you try to tame when you have an active pet out with you, you get the message that “You have too many pets already.” as you always have. But dimiss that pet — don’t abandon it, just dismiss it — and you can tame another. The dismissed pet then disppears. Sort of.
The first time I tried this today I tried it on my main, who had three pets total (two in the stable and one with me). After taming the new pet, I went back to the stable. The two pets who had previously been in the stable where still there, but every time I moved a pet into or out of the stable I saw my ‘lost’ pet very briefly, both in the pet UI window and in the world, next to me.
So I tried this again, on an alt who had two pets (one in the stable, one with her) and a stable slot open. After taming a new pet, the ‘lost’ pet was in the empty stable slot. At first I couldn’t access it — even when it showed as being out with me it wasn’t there and I couldn’t call it. But after switching the pets around in the stable slots a few times, it suddenly appeared. It seemed to be okay — functioning properly — and continued to exist after I relogged.
So … it seems that I just managed to tame a new pet without losing my existing pet and without stashing my existing pet in a stable first. If this is indeed a new feature, it is a very convenient one. If you are out hunting and you see a pet you must have, or a pet with a skill you need, and you have an empty stable slot, you can dismiss your good pet and quickly tame the new one without losing your old pet. But if this is a new feature, it seems to be a bit buggy — I suspect my ‘lost’ pet on my main is still there, somewhere. And I wonder what happens if you don’t have enough stable slots but you buy one later? I should go test that!
EDIT: Yes, my ‘lost’ pet was still there! After I abandoned the temporary owl I tamed, I was able to pull the spore bat back out of the stable (leaving two cats in the stable). More than that, I was able to stack multiple inaccessible pets in my stable — at one point I had two cats, a spore bat and an owl in the stable (although I only saw the icons for the two cats) plus an owl out with me!
EDIT #2: I found an alt who had only purchased one stable slot instead of both. I stacked a pet in the one stable slot she had (that is, had one in the stable and one with me, and then tamed another) — then purchased the extra slot and was able to move that third pet into it.
You know what? I think this might be the ‘way to train skill when you have three pets’ they’ve been promising us!