There are different reasons why QBs are in the HOF. Namath is there because he was the first real star in the AFL/AFC and won a Super Bowl. It probably helped that he played in New York. Len Dawson may be there because he was an AFL star. Bradshaw, Starr, Staubach, Aikman, Elway, Griese and Montana are there because they were great leaders and won big games not necessarily because they had the best stats. Marino, Favre, Unitas, Fouts, Tarkenton, Moon, Kelly, Jurgenson and Y.A. Tittle were inducted mainly because of longevity and stats although some did have Super Bowl titles. Some of these guys had 17-20 years in the league and led the league multiple years.
Right now I don't see that Kurt Warner has done enough in any way. He doesn't have enough consistency with impressive stats or enough championships.
I would almost compare him to Steve Young. Young was 30 years old before he got a chance to really show what he could do in the league. He only had 7 years in the league when he was full time but in that time he was dominant and finally winning the Super Bowl solidified his HOF status.
As I stated earlier I think Warner could be considered if he somehow wins another Super Bowl and puts together a few more productive years with the same team. Right now he will fall into the same category with Jim Plunkett, Vinny Testaverde, Drew Bledsoe, Mark Rypien and other good QBs that will never be in the HOF.