I think the prediction was that we could see a summer sea ice meltout by 2016 +/- three years.

If you look at this year's sea ice volume (volume, not extent)  it's clear that we could see a melt-out this year.  All it would take is the sort of summer storm system we saw in 2012.  Volume is very low for this time of year.

If the world's coastal cities have to be rebuilt inland?  Do you have any idea how much that would cost?  

The climate has always changed and will change aside from what humans do.  But this time the change is extremely,extremely rapid and it's all on us.  If it weren't for humans the Earth would be very gradually drifting into another ice age hundreds of thousands of years from now.

We've reversed the natural change in less than 200 years.