I dont think Wariner will never break the 400 wr. A few tenths at that pace is significant. 43.45 is over a quarter of a sec slower than MJ's WR. Wariner doesnt have the raw speed, he wins on maintaining his form through the whole race based on strength/muscle endurance. His lack of raw speed will be the limiting factor that keeps him from a WR.
Also, this will probably be the weakest Oly 400 in recent history. He's been racing without stellar 400 comp for years now. Back in the Steve Lewis, Watts days he would have been challenged just to medal.