Well on the DVD, Mario said that if a 4th segment was made he would want it to be about Sonny and how he grew up from a tenderhearted little kid to a murderer. Perhaps someday his wish will be carried out.

"Mio padre se chiamo Antionio Andolini, e quisto e per ti!"
http://blake.prohosting.com/awsm/script/THEGODFATHER.txt
http://blake.prohosting.com/awsm/script/godfather2.html

2003 Predictions:
Yankees win World Series over Cardinals in 6.
Osama bin Laden killed by the USA.