What is this?
When clicking the name I'm not seeing anything different. It still shows the realms off line. In fact, it's the only option. Now my memory isn't completely clear here, as it's something I've always just clicked on, but for my U.S. account the options there have always been "United States" and "Oceanic." So what's this new tag about? The only time I've seen this has been on the PTR.
I have a few guesses.
First, and quite likely the most plausible explanation, is that it is an artifact of the servers being upgraded. Blizzard takes the servers down, the put them into a special mode, and they update them as needed. That could be all this tag is about.
However secondly, it could be for integrated patch testing. We'd no longer need to download a separate client. This is possible, and indeed wise, since all of the patch files are stored in a database like system. Within that, could this be the gateway to Wrath of the Lich King beta testing? It's a stretch, I know, and I'm sure some of you are going to flame me for even mentioning it. However, it's a possibility.
Finally, and I think quite likely in its own way, is this is where they'll store the tournament servers. While several of us have gotten used to the Tournament Test Realm (TTR) being up for the past month or so, the vast majority of WoW users probably don't know about it yet – or the PvP tournament. When the tournament does go live, my guess is that the servers will go in here. Perhaps they'll rename the category by then to something a little more descriptive.
There is literally no information out there on this. Belfaire says in a forum posts asking about this "Give it time." After this comment is a lot of QQ and conjecture by posters. They all claim to know something, and they all claim to know something different – so that what you read there with a grain of salt.
Basically we and everyone else haven't anything but educational guesses as to what this is. It's an interesting little spark, and we'll keep you updated as more information becomes apparent.