Looks like a new facade around the existing Madison Square Garden, with a heavily-remodeled interior in which the upper level (as it exists today) is removed to gain space. I'll guess that the "lost" floor space has been taken up by the new Moynihan station across the street (taking over much of the old post office).
Actually looks nice if they can pull it off.
I spent much of my 32 railroad years going in and out of there. I even have a memory (as a teen, long before my railroad days) of what was left of the original station before it was demolished...
