Seeing as it's Ford Field, and the WrestleMania 23 logo seems to be modelled after an automobile, I think they might have guys come to the ring in cars.
They should reserve the cart entrance for Champions, in my opinion. It'd make taking a Championship into WrestleMania seem like something special.
The main events will likely get special introductions for their participants, like last year. John Cena's "pre-entrance video" will likely compare him to a machine. Show a Ford being assembled and compare it to John Cena. Shawn Michaels will be exciting. Maybe show his past achievements at WrestleMania set to "Sexy Boy" before he ultimately enters to the DX music.
Those kind of elongated entrances make WrestleMania a little special, in my opinion. It would also be special if it weren't full of sucky matches each year, either. Trish Stratus vs. Mickie James, Edge vs. Mick Foley and the Money in the Bank Ladder Match were the only matches I liked last year, if memory serves me correctly.