I found a location North of New Vegas called the Northern Passage but I can't find any way to get inside the cave.. Theres an inside cell marker but no way to reach the entrance.. bugged?

Not a bug. Its most likely reserved for a DLC down the road

Way to tease us Obsidian >.>

Yeah, got stuck there too. Intriguing how they do that...

I toggled collision to get past the rocks and was able to get inside, and when I did I found a surprisingly long mineshaft-like tunnel that led to an opening where a door should have been. It was clearly unfinished, but I found it odd that they made an interior for it at all considering they'd probably change the interior whenever they used it for DLC.

But yeah, it's clearly meant for a DLC, and I'm a little insulted by it to be honest. Letting your fans know that you already had DLC planned far enough back in development that you added it's entrance to the game before releasing it isn't exactly a wise thing to do. People usually get angry over that sort of thing.

Canyon Wreckage also blocks the path to the huge area of map that is unused. I doubt that's for DLCs though, as the blocked of area is enormous. As in, as large as the area that is explorable. If DLC hadn't killed the expansion pack, i'd expect that to be used for one.

I think the consensus of speculation is that this area is the entrance to the Lonesome Road DLC, seemingly hinted at by the Dead Money DLC, and increasingly thought to be the next to be released.

If so, i doubt all that area is going to be used. It is humongous, you can run 10 minutes in one direction and not fall off the map.

Guess I don't understand why they would not have utilized the extra space on the map if they weren't going to use it for DLC. I personally would like something expanded on the existing map (like the area mentioned above). Wouldn't lose my equipement, nor your companion. I don't like how they always send you to a different "map". IMO.