It does make a difference when a QB used to throw for 3,000 passing yards a season and now they can throw up to 5,000 yards a season. That's a lot more opportunities in the pass game for the rookies, and a main reason why they are breaking out quicker than ever. Some don't make it still, but they get a lot more chances, and if they have the talent, they will show it every game with extra targets and hopefully receptions when they haul the ball in. They may take just as long to adapt to the NFL, but their impact will be bigger because of the larger emphasis on the passing game if that makes sense. If Cain or Fountain show they can handle the workload, they will get plenty of opportunities, especially if Luck throws for around 5,000 yards and is healthy. I would expect either Cain or Fountain to get 800+ yards receiving their rookie year.