And yet the Sixers’ plan also shows how much has changed since the Rendell era. The arena is a small piece of the project. Rather than pack Penn’s Landing with entertainment boxes, the franchise’s wealthy owners Josh Harris and David Blitzer are focused on creating a mixed-use neighborhood that is largely attuned to the spirit of the 2010 master plan. The proposal was even prepared by the planning consultant that cowrote the waterfront master plan, Cooper Robertson. In their submission to the DRWC, the Sixers promise to bring thousands of apartments, a hotel, two museums, a dozen or so restaurants, a supermarket, and a new public school — along with that 19,000-seat arena — to the Delaware waterfront. Some parking is envisioned, but most would be tucked out of sight.