Madden on the PC uses it's own graphics engine that has nothing to do with the consoles as it uses directX. So Madden 07 will still use directX9.0c for it's graphics. It should look similar to last years game, which looked really good anyway.
I hope Madden 08 is the one that makes the graphics leap and will probably get an overhaul with Vista and directX10. If you've seen the game "Crysis" which is in development it gives you an idea on how great PC games might look in a year or two.