Anyone who thinks Sara Hall is in Gwen league does not know enough about being a top world-class athlete. Gwen destroyed the competition and made them raise their game a bunch. She won 13 straight ITU races, where all sorts of things can go wrong. Probably the only times she has really raced the 10km hard is when something has gone wrong and she is not in the first bike group on the road; I think that she has run somewhere in the 32s. Since she would have had to pull her group much of the time, the bike leg would have been pretty hard (and the swim is never a piece of cake). I would be surprised if she does not hit 31 for 10,000 if she runs one with peak fitness.
Not many people can average 40-50 miles per week, with a peak of 57, long run of 16, and hang with a world-class field for almost half of the NYC race. She was not interested in running a safe first race, she wanted to know what it is like to be at the edge, and she has been on the physical edge more than at least 99.9% of the posters here, so she knows what it takes and many commentators here simply do not; watching others is just not the same.
I actually traveled to that Big Ten Indoor meet where she won the 3000/5000 double (and I think that she was Athlete of the Meet, not sure). And she did that on 18 months of training after not running for three years and being a top student in one of the tougher majors at Wisconsin. When she has run she has the muscle strength for the swim and even the bike and will be able to knock off that weight without doing anything but training. Bowerman is a natural for her, with her Wisconsin ties, and that womens group has gotten really good (NYC, SC Silver, Bronze, Silver, 5000 Bronze, 10,000 Silver) and it has given Jerry the background to know how to transfer what he knows from men to the women. He is very good at differentiating across athletes, although some promising runners just don't work out (Uhl, the Canadian).
As for knowing how to race at the very top of the sport, not of the next best Americans can hold a candle to Jorgensen. She went down in London with the water and maybe a flat and got left behind. She then was still pretty much a neophyte and got better really fast. She has more hard two-hour or more races under her belt than any American distance runner, maybe as much as the top several combined. She is meticulous, she is driven, she will not have the complications of travel, season training sites around the world and the family will get her out of the training world for a balanced life. For sponsors, I doubt here Tri contracts like Roku or whatever are a big deal, and will constrain her.
The notion that her chances are 1 in 10,000 are really off base. I would give her a a pretty good chance to get one of the three slots for the OGs, and since she has raced so often in warm/hot/humid weather she knows much better how her body responds to that kind of stress than the other American marathoners. Unlike almost all running neophytes she knows all about how her body handles fluids and fuels and how much she needs because she has many more runs at it in race situations than anybody she is competing against (Although Shalane and Amy probably are not too far behind). She will never be nervous in a crowd as she deals with that on the bike for an hour a race with much worse consequences for errors. Yes, we have not seen how she will react to marathon training, but thinking that she will have a hard time cracking 2:30 is silly, and she is a racer, best in championship races, not a time trial type so may never have a truly fast marathon.