Since the building is still being designed, nobody but those involved in its development knows for sure, but the assumption is that it will be like the St. Regis across the street. There the existing building was gutted and the the interior of the new tower was integrated with a new interior for the older structure, but no significant changes were made to the exterior of the historic building (except I believe the old cornice, thought to present a seismic risk, was replaced with something that looks identical but is less likely to fall off).