The Prudential Center does about 90 dates a year.
The Staples Center is home to 4 professional sports franchises, they can easily operate without any concerts or events. If the Prudential Center were home to the Devils, Nets, Islanders and Liberty, they wouldn't need any concert bookings either.
Between the money they get from Prudential and MSG, plus adding the Nets for a few seaons, they should be able to stay afloat for the next few years. Things certainly have not played out the way Vanderbeek and Gilfillan envisioned though, and they probably aren't the owners five years from now.