Here's the image of it when all the work is done. As can be seen, the third floor and the nice roof domes of the original design will be re-constructed.
I take many domestic trips on Shinkansen from here. The original brick building was built in 1914. I've heard that the design was a copy of the Amsterdam Central Station, but guess it has been proven wrong. The construction causes automotive traffic congestion every day. I look forward to the day it is all finished.
Here's more about the renovation.