Well, since the first expansion is focused on new content on the moon, wouldn't it be logical to assume that whatever is locked away on Earth would not be a part of that? I mean, one would think that if there was going to be a smoking gun here that there would be similar areas to glitch into on the moon, but that doesn't appear to be the case at all. With the second expansion said to introduce the Reef as an actual area, that doesn't seem to match up with those areas, either.
So what is the stuff that's on Earth right now? I see a few possibilities right now:
1) They're areas being prepped for a different expansion that's focused on Earth. How they plan on doing this would be a mystery, since they haven't mentioned any DLC plans beyond the two announced expansions.
2) They're areas that were, at one point, part of the normal flow of the game, but had to be blocked off since they weren't able to be finished in time, and Bungie doesn't have any plans of finishing them off. They would have done a piss-poor job of hiding those seams, so to speak, but that wouldn't be too surprising given what we know about the Grimoire stuff.
3) Similar to item 1, they are being prepped for a different content roll-out that will be tied to an in-game event where they're unlocked for everyone at the same time and there's no money involved in it. Unlikely as that sounds, it's pretty common for that to happen in the MMO sector, and the areas right now don't seem substantial enough to justify a new expansion.
At the end of the day, though, I don't see this as proof of the content for the expansions already being in the game. There are likely some foundations to be discovered, but nothing to the point where people who can hack the game would be able to play it in a manner remotely identical to how it will eventually turn out.
