Kurt Warner won the Walter Payton Man of the Year Award, which is awarded to the a player who has had a positive effect in the community. I think he wants to do more for his community. That's one of his factors in his decision.
The Cardinals' have there "franchise" quarterback in Matt Lienart. I don't think Leinart is going to pan out and should have entered the 2005 NFL. Lienart also wasn't Whisenhut's guy, it was Dennis Green's. I don't what the Cardinals are going to do with Lienart, but he better be worth something.
Kurt Warner is 37 and doesn't have many years left in this league. I question whether he can compete at the same level as he did last season. His arm won't be able to have the same velocity or accuracy, so he may want to retire.
If Warner retired, he wouldn't finish his playing career on a good note. Losing the Super Bowl to probably the best franchise isn't the greatest way to call it quits. He may want to play another season and maybe win the Super Bowl.
In the end, I honestly don't see Warner returning. He is just too old and won't compete at the same level as last year. He will be happy after his career, helping his community out. If he does retire, I see them drafting a quarterback in the 2nd or 3rd round like a Nate Davis of Ball State or Nathan Brown of Central Arkansas. Free agency could be an answer, if they could get a guy like Brett Ratliff or Brock Berlin.