Edit: Turns out it is on a private server, as pointed out by “Rofl”. Oh well, we can still dream of an easter egg like this 
A video showcasing high level abilities was just released today. Although it isn’t official Blizzard Diablo 3 media, it still looks legit. and even if it turns out to not be legit…it still looks awesome and gets your more excited for Diablo 3 than ever before
We see a lot of PBAoE skills, which are really good for farming items and gold and we see them on all the different classes. They look pretty effective at clearing out the mobs, so either the character build is built around the abilities or they are heavily runed…which you can also argue is a form of a build
It looks to be in cow-level, but with zombies instead. Having access to a level, where you can kite and AoE mobs would be insane for farming. Especially as the loot drop tables are constructed so as not to be useless outside of boss drops (to avoid farming runs on high level bosses). You will get the best loot and gold from random elite packs, so hopefully this secret level will have some of those thrown in. Even if that isn’t so, you could still load up on magic and gold find equipment, and still make a killing on the gold alone.
Wow, Diablo 3 release in a little over a week. I am super excited!
This is not a secret level. Its just an area in Act one on a diablo emulator.
ah well, something seemed off about it. Guess that was it
But let’s just hope someone finds an Easter Egg like that!