Maybe a Lost easter egg SPOILER 

rather then a city skyline it could potentially be the survivors standing in a line. or it could be absolutely nothing.

Interesting

I think its to show the 'life' after the island for the Oceanic 6. As in their life is in the city now not the island...

is does look like it is meant to be somthing cant tell what though could be the people dont think it is a city skyline

I think its because theres now flash forwards and there gona be in the city and stuff.....

I also noticed a 4G in the corner.

That would be a natural human inclination to find recognisable objects in images (e.g. faces, numbers, letters.)

if youve seen the new poster, it has the island and the trees over the water, but the reflection of the trees is supposed to look like the city skyline so i think its meant to be a city

Well, it's deffinatly something! It could be a city skyline... I wonder that has soem bigger meaning... hmmm....

Thanks for posting!