Testing Battle Pet Cageability and Quality In MoP Beta

As far as I know, the original post said that they would become rare in a future build, not that it had been implemented yet. There are some things that can and may be left until the last minute or even only seen once the expansion goes live (most professions, for example, aren't seen in their truly final state until an expansion goes live).

There are some things that are simply more important to test than others, particularly if it's just a matter of tuning. Raid testing, for example, is almost always either under- or overtuned because the tuning's the easy part, the part they can do purely internally, as long as the mechanics work right and the fight is bug-free. I think we'll see something similar with per stats and qualities.

Also, whenever they do get around to implementing the change, there's no reason caging a pet should "turn" it rare. Pets should always be the same quality in your journal as when caged.

Generally, when Blizzard says they plan to do something, there's little reason to assume they won't. Of course, some exceptions apply, like the infamous "all glyphs will be learnable from research come 4.2" blue post that never actually came to pass. Still, particularly at this stage, and with something that should take about as little programming effort as changing an ilvl, there's no reason to doubt them at this point.

Of course, as always, one should stay on one's toes. Contingency plans and adaptive reaction once Mists launches will be far more important than any kind of assumptions made on beta data.

I just been playing beta a few days and today maybe on my 5th pet caged I got a rare blue small frog and the achievement "a rare catch" maybe it had something to do with the restart? Or just lucky.

When he says rare pet it means in your pet journal it's marked as rare. I'm not sure if it will be rare when it's caged or when it drops. Pets like the Captured Firefly are currently common (white) items but are a very rare drop.