The Architect's Newspaper has the details on what all this might look like. According to the story:
The Department of Design and Construction (DDC) has commissioned Deborah Berke & Partners to complete a $16 million renovation of the aging structure and bring it up to current code requirements.
While the crux of the commission involves upgrading the 1894 building’s outmoded ingress/egress routes and substandard mechanical systems, Berke also saw the opportunity to improve the interior and how it was organized. The center’s primary inhabitants — PS 122 Gallery, Performance Space 122, and Mabou Mines — all grew into their rooms organically over the years, without much thought about how they functioned as a whole.
The architects quickly determined that the most economic and elegant solution was to place the new elevator, fire stair, and mechanical ducting within a tower addition situated in a yard to the north of the building. “Typical of a 100-year-old building, it has a fragile structural system of terracotta arches between steel structural elements,” said Jones. “You can’t just pop holes in that.”
Consigning these upgrades to the add-on pavilion also preserved the historical character of the original building, which was valued by tenants and the DDC. To minimize its impact, the addition will be constructed of light and luminous materials. The tower itself, a steel structure, will be clad in glass with a perforated and corrugated stainless steel scrim. A canopy and marquee that jut into the street, announcing the new entrance, will also be of glass and perforated steel.
The construction is expected to be done by the summer of 2013. So three more year's of the sidewalk shed on the corner. At first glimpse of the renderings, this looks like an awkward marriage of the old and new...