If Zac Efron plays Light Yagami that would be perfect. Zac actually cosplays as guess who... Light Yagami. Now I could see Tobey Maguire (the guy how played Spider-Man) playing L Lawliet, and nobody else. I could also see me as that extra in the second Death Note live-action, you know Death Note: The Last Name, that dies because he tells people to not follow KIRA because Misa was killing non followers of KIRA.
The only reasons I wouldn't see it is if I don't have the money, if it goes straight to DVD or Blu-ray, and/or if they change everything about it.