The roads are a tough issue, especially getting through the tunnels. With that said, people will stay in rooms all the way to Cleveland if they want to try and hold hotel rooms as an obstacle. I remember the SB in Tampa and I lived in Orlando. The rooms in and around Tampa were all booked. People were staying in Orlando and many other cities in Florida and driving in to the game.
Sure people will stay as far away as Cleveland if they have to (Monroeville will be far enough actually) but by the time they get to Heinz Field the game will be over. Tampa, Orlando, most resort cities have roads that are 6 to 10 lanes wide. Every road into and out of Pittsburgh is 2 lanes each way, max. Because of the hills, rivers, tunnels, and bridges, you can't fix that. Ever.
I get that the stadium sells out now and Sunday traffic isn't horrible but with a SB you have a lot more than just spectators, you have more media, sponsors, events, hookers, etc.