No reason for Rupp to run a marathon. He's a medal threat over 10K in the next worlds-olympics-worlds cycle.
He's just had his best competitive year ever over 5K.
Leave the marathon to the marathoners.
Rupp is a bad boy on the track. Let him continue to excel there.
By the way, look for Eluid Kipchoge to pick up the Olympic marathon gold.
He started his career with a worlds 5K gold. He's since picked up Olympic bronze and silver medals. Eluid is the man to beat in Rio. But he'll win gold. Complete his collection of Olympic medals.