The US marathon team isn't really strong this year with Young/Mantz/Korir unlikely to medal. Bekele last 2 races have been master's WRs, so he looks like he's finally training consistently, although 2:04 is a long way from 2:01. Kipchoge hasn't looked great lately, but he's less than 2 years off setting a WR, and there's no reason to think he couldn't still run close to his best if training has been going well. Assuming Kipchoge and Bekele have both been healthy, they can probably run at least 2:03 on a good course. Alas, Paris is not a course for fast times.
The hills are more comparable to cross country than to marathoning. One might expect Mantz and Bekele to do a bit better comparatively due to their (very) respective success at XC. One might also say that XC success has nothing to do with how someone handles a hilly marathon, and it's not like Bekele is any more successful in hilly marathons than Kipchoge. The wonderful thing about the Paris course is the hills are so extreme that there's no way to know if either argument holds any water until we see them race. There really is no precedent for this course.
The hills are so crazy that basically anything could happen. The hills are all in the middle of the race, and there's no extreme elevation change for the last 6 miles, which is 'when the race really starts'. It's not at all inconceivable that Bekele and Kipchoge go out in the lead pack, hit the hills way too fast, then are overtaken by Conor Mantz in the pain cave. Particularly because that exact thing almost happened in Boston last year. Of course the Americans could bonk too, but I feel like there's a good chance at least one of them tries to run their own race, whereas Kipchoge and Bekele will want gold or at least a medal.
I think there's a better chance that they both finish behind the top American than either of them medaling.