47.45 is about where he should be at. I think I said in another thread that he'd run 47.47.
The formula I've always used is 2/3 of your 400 plus 1/3 of your 1500 will give you your 800 time.
Based off Nick's times of 47.45 and 3:36.06 it works out at 1:43.64 which is not that far off his 1:43.76PR.
Keeping this in mind, Rudisha off his 45.50 and 1:41.01 PR's it indicates that he should run around 3:32.03 for the 1500. Just shows you how good you have to be to run 1:41!