Just realized...Rupp attempted to qualify for the 5k/10k/marathon in 2016. That was fun. I could see him trying in the 10k again. Training for the marathon will probably take the sting out of his kick, but he could still try and win - then give up his spot if he does (I agree with another poster that he shouldn't try the 10k at the Olympics, assuming he makes it). Racing a hard 10k during marathon training is not unusual. Also worth considering what the 10k will look like at the 2020 Olympics. Who will be the #1 10k runner in the world at that time? I think he's 100% running the marathon, just interesting to think about.
Also what about Ben True? I could see him in the 10k.