The history is fairly clear, but it's hardly fair to say PP "fell off a cliff". He had Syracuse as a top 20 team for 10 years, then it fell to a top 50 team his last 3 years. After he left it fell further to a #100 team for 4 years, now they're fighting their way back to #60. It looks to me like Syracuse fell down a hill and PP did a fair job of suspending/delaying/minimizing the fall. Once he left, they went to the bottom of the hill.
Personally, I don't think it will be that easy to replicate what he did at Syracuse in his first 10 years. With the Internet there's more visibility to northeast high school players, and it's easier than ever for coaches elsewhere to make contact and fly here. Recruiting budgets and travel budgets for recruiting are much bigger with all the TV deals, and air fares haven't increased. There's no longer a big pool of under-recruited northeastern players, and kids aren't necessarily as attached to staying local for college. The Internet and cheap air fare have made long-distance travel seem more normal. The unsettled conference situation is another problem.
I still think he's an outstanding coach, though, and I think if he can win some recruiting battles then he'll get us sniffing at the top 25 every other year or so. If we can be consistently as good as WVU has been or Louisville will be this year, I think we can be very pleased.