Kind of a bummer that this thread has digressed into a discussion of Rupp being clean or not. I suppose it is an important, though near on impossible, question to ask...
As far as his chances at this record, I have long considered the half marathon to be rupp's best event. While he has shown tremendous track ability and I'd wished he stayed there, his early endeavor at the event in NYC, where he got tangled up and fell, where he managed a 60:30 was quite impressive. I see him having a strong chance so long as his form comes around. His recent performance at the Turkey Trot in Manchester was lackluster to say the least. Rupp should be hopefully making strides since then and houston is still a few weeks off. While I believe the CR is Feyisa Lelisa's at 59 low, I know Desisa did run it in recent years as did Meb and I believe neither broke 60 despite winning the race. It will take good conditions and strong pacing early for Rupp to get the record. I wouldn't be surprised if he came up short and ran just around 60.
Lets put this run in perspective though, the question isn't IF Rupp can get the record, it's when. If a guy like Estrada (27:30/2:13) can run 60:50 at Housto, then Rupp, who is many minutes better over the marathon and 45 seconds better over 10K, should easily smash 60 and give 59 minutes a scare.