As much as I love this proposal, I don't see it coming to fruition. I know its supposed to come in different phases, but the problem isn't the proposal itself, but its really the fact that every time some proposal comes into town (the great American Commerce Center which would've given the city the tallest tower not only in PA, but in America for at least a couple of years until the Freedom Tower is fully erected is one, as well as the old Center City Tower, which would've been Comcast's HQ, the SLS hotel on Broad and Spruce, and the Mandeville Tower, and the unfinished Waterfront Square), it either never gets built, it gets delayed like the SLS, or in the case of the ACC, it goes through red tape, NIMBYism, bureaucracy, and corruption and corporate welfare a la Comcast, so that proposal dies in favor for another corporate tower like the CITC.
The problem with Philadelphia is that although it's a beautiful city with a lot of amenities (the Art Museum, Fairmount Park, South Street, Manayunk, South Philly,and the SportsComplex), the city still has a major inferiority complex and it's business structure and its business taxes are going to be a major hindrance in getting this entire proposal into reality. I was a major booster for the ACC, and to this day, I believe the had the ACC gotten built, it would not have just radically changed the face of Philadelphia as a major world class city in America, but it would've helped Philadelphia with it's economy as well since the ACC was designed to attract a major company to the city.
Philadelphia cannot survive on the backs of Comcast alone. I predict Aramark might leave the city in the near future to Washington DC or some other city, we couldn't retain Santander (formerly SovereignBank) and they leave to Boston, and Crown Cork and Seal might go the way of being a subsidiary like Pepboys and Rohm and Haas are!!! As long as we have the tax structure that Philadelphia has plus the nimbyism, the negativity, the corruption, and the parochialism that permeates Philadelphia,since the ACC couldn't get built, the Schuylkill Yards is only going to be a huge figure of our imagination!!!
I'm currently in SF, and the city doesn't need a huge skyline like NYC and Chicago, because it has many hills and views which is it's strongest points plus it has a great troll and light rail system (Muni), and an even better, albeit expensive commuter system (BART), which links not only Oakland, Berkeley, and Richmond, but will link with San Jose in a few months , as well as commuter rail lines suck as Caltrain and even commuter rail lines gong from San Jose to Sacramento, and even Marin County has its own commuter rail system. The Bay Area is light years ahead when it comes to not only retaining businesses like Wells Fargo, TheGap, Levi's, and Uber, but it has the best mass transit system in the West Coast, and is on par with NYC, Chicago, Boston, and DC when it comes to total infrastructure.
Philadelphia had a great mass transit system with the PRR and the Reading Railroad, but once SEPTA came to be, those diesel lines going to Allentown, Bethlehem, Easton, Reading, Lancaster, and West Chester have been mothballed and won't even come back because PA is a very parochial and cannibalistic state which doesn't even prop up it's biggest city in favor of rural areas. If Philadelphia doesn't get dropped off the Top 10 American cities by 2020, it's definitely going to happen by 2030!!!