It won't melt unless it floats off to a warmer climate. IF it does, it would take many many years to do so. It won't have any impact on seaboards for a long time, if any impact at all.
How high will the seaboard rise when the recently broken off Antartic ice berg melts?
The Connecticut-sized berg was fully afloat before it broke off, so if you understand anything about physics, you'll see the total ocean volume will remain unchanged.
The worry comes when land-based ice, not part of the current ocean volume, begins to melt into the ocean. Glaciers. An ice shelf such as the one "calving" this huge new berg is a buffer/barrier that prevents the descent of glaciers into open water, which adds significantly to ocean volume. This is what is happening on an unprecendented scale in Greenland, in the North. Not only do sea levels rise, but ocean currents can be disrupted by the influx of cold water, which influences the weather of entire regions, and salinity levels are reduced, which could present peril to sea life.
Now that ice buffer in the south is smaller.