It's more or less clear that the "secret project" is a progressive Vanilla realm.
There are several indications across multiple threads. You just need to pay attention.
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I have 5 full level/full gear characters on MOP that I play once in a blue moon because there's seriously not enough people to do anything. The last time I entered, there were both horde and ally in one place talking through /me, so that's how few people there are.
Now, I don't really care what they do, but I wish I had a reason to play. If they aren't gonna attract players to MOP, might as well allow us to get out with some kind of compensation. I personally think MOP is beyond saving, but I don't feel like starting from scratch anywhere. I've already lost years of hard work thanks to the infamous Hermes situation, so I'd rather quit entirely than start from 0 again.