The thing about Deena Kastor, is that she is the one runner that can afford to run 5 minutes off her best and still win.
Unfortunately I think she might be a little more than 5 minutes off 2:19 fitness, but perhaps still good enough to make the team.
About the others...
In my mind, Kara Goucher ran her best marathon on her debut when she ran 2:25 at NYC in 2008. Given the nature of that course, that probably translates to 2:24 in a fast flat marathon. However, given recent setbacks, I doubt that Kara is going to be at her best, perhaps 2-3 minutes off that pace.
Flanagan has only run a single marathon, second at NYC 2010 in a race that had a slow first 20 miles and a fast finish. If we try to imagine where she would have been if she ran NYC in 2011, she might not have been in the first three places, but I really can't imagine her being much behind Ana Dulce Felix and Kim Smith who ran 2:25:xx - I'm sure Flanagan can also run 2:24 on a fast flat course if she's having a good day and unlike Kara, she seems to be heading into the trails in top fitness.
Desi Davila ran 2:26 in Chicago and 2:22 in Boston, but the wind was obviously a factor as it was for Caroline Kilel who went to NYC and ran 2:25 high. I'm guessing 2:24 on a fast flat course might be realistic.
So if Flanagan and Davila are having a good day, they should be safely on the team, but either Kastor or Goucher are going to miss out.
Someone else could surprise and make the team ,especially if both Kastor and Goucher have a really bad day.