That's a photo of the cabin Hurley saw...we don't know that's the same cabin known as Jacob's. When Hurley saw it is was in a clearing, had no ash around it, and he said it was in a different location than the cabin Locke led them too...which was by trees and had the ash.

I couldn't get a clear picture to post of the outside of the cabin during the scene where Locke and Ben went to visit, but the second one I posted is of the one where Ilana and the group went to, obviously expecting to find Jacob there. It also had the ring of ash around it, so it's the same cabin, even though it's moved. The pitch of the roof is the same all of the times we've seen Jacob's cabin; it's different in Rose and Bernard's cabin.

It makes sense for Rose and Bernard to build a cabin during their three years on the Island. All they need is each other and for the Island to continue Rose's cure. And it makes sense for Jacob's cabin to be the one that Horace was building. After all, Locke found it by locating the blue prints and map after Dream Horace directed him to, so Jacob or Anti-Jacob directed him to the cabin through the dream. (One of them also influenced Locke to find the Beechcraft through a dream as well.)

The ring of ash seems to keep its occupant inside (whether it was Jacob or AJ), though it doesn't seem to keep the cabin from moving or appearing in another place (as it did with Hurley, though it's not clear whether this was the cabin physically moving or some sort of image projection). However, during Locke's second visit, he saw the ring of ash in the first location, though no cabin. He then found the cabin from Horace's map, so it was in a different location than when he first visited. We didn't see or hear anything about the circle of ash on this visit that I recall.

I'm not so sure that Ilana's group was expecting to find Jacob at the cabin we saw. Since Richard took the Others plus Sun and FLocke to the temple, where we first saw Jacob, I don't think Jacob ever lived once was at the cabin. Only Ben said Jacob lived there...and we know Ben lied.

I think Ilana was expecting Jacob at the cabin, because when she sees state of the cabin she tells her people that Jacob hasn't been there for some time and that someone else has been using it. So it seems that Jacob was associated with the cabin at some point, and that Ilana's group knew about it.

Wrong. If that were the case Everyone would be incinerated... and gee, I don't think that would make for a very interesting Season 6. I believe Rose and Bernard will jump through time along with everyone else from their time period. I also believe the flash of light was that time jump and not the bomb.

I do see a difference in the pitch of the two cabin roofs. Also, Rose and Bernard used palm fronds to roof it, unlike the other more conventional roof.

I'm not convinced Rose & Bernard jump forward along with everyone else. There's a part of me that feels like the island actually sends them back further in time and they're the skeletons found in the cave... but... who knows lol. They seemed rather content to not be involved with everyone else.

I do believe Vincent the dog will flash to the present of 2007 though... he's the only one that's been confirmed to make it to the finale

Instinctively, I think Rose and Bernard's cabin is the same as Jacob's cabin.

Rose and Bernard's cabin exists in the 70's. Wasn't Jacob's cabin (built by Horace) built closer to the time of the Purge?

No she didn't. She said "he isn't here."