Okay, we aren't allowed to post any pictures so please don't as i don't want this post removed.. however feel free to discuss this topic as this is based on already announced information but all the forum topics i read seemed to forget it.
The idea is that Kezan is level 1-6 as well as all of Gilneas being level 1-15, including a lower section you did not see in the leaked pictures which only contain zones in either pre-phase states or post phase states.
THe goblins flee Kezan at level 6 - and the story continues, you flee Kezan thinking it is lost though, you don't know what happens to it. Your sinking ship is rescued by other goblin profiteers and ultimately the horde when your arrival on the Lost Isles (level 7-15) is challenged by the alliance.
Gilneas gets sunk, well half of it does, this is the part you haven't seen in the pictures, and the rept of level 7-15 continue on the upper half, then you leave with the night elves via boat, and like the DK starting area, this level 7-15 version of Gilneas is forever lost.
This brings Gilneas to a new phse, Lost isle remains unchanged. NEw phse Gilneas is high level they said at Blizz con, there you partake in a fight against the forsaken, i.e. horde join the forsaken and alliance the Worgen.
But this was blizzcon, and they may have long since change d their minds, so clarification is requested. I suspect you will also be able to go to a high level of KEzan, to discover the earthquake did not destroy the Island completely. Question is does it return in Cataclysm as a high level zone? or in the next expansion as the Goblin Capital.