I am not a 2:18 marathoner, and never was one. I was never good enough even to have a chance at becoming a has-been. But if we apply the "if you haven't done it, you can't comment on it" standard consistently, then pretty much all commentary on all things will cease. Perhaps that would be a good thing, but we are in this world rather than that fictional world. So ... seems OK to discuss and to raise some questions, and wait for the OT for the answers.
If I were predicting, I would not pick Cabada to make the USA marathon team, but I would think, if he ran well he would be top 10, and there would be a payday in that (10th place earns $7000) . He ran 2:11:36 for 7th in the 2012 OT, and he ran 2:11:53 for 11th at Berlin in 2014. Assuming good health, good preparation, and good racing, top 10 is a reasonable estimation for a 2:11 guy, and -- on the day, who knows? If he needs to earn his keep winning small races for a few thousand $$, then he has the talent for that, and could do that, a lot, post marathon trials -- there are enough of those races around for him to do so. Making a living, or part of a living, as a 2:11 marathoner is not easy -- I respect any athlete who is dedicated to that, and who keeps at it.
I know we can go back to earlier eras of marathoning and find studs who ran top-level races close in time -- Shorter, Beardsley, et al. And yes, I am aware of Kawauchi, and I am impressed with his high-frequency, high-quality racing, but he is a 2:08 guy, and one thing his high-frequency racing has done is ensure that he is never going to get that close to 2:08 again. Kawauchi and legends of the past aside, we generally don't see today's 2:04 (and those few who are faster) marathoners, who are aiming for top-level performances at major marathons, running around 2:11 a month before as a tuneup. That's pretty much what Cabada did here, and if he runs a near-top-level performance (for him) at the Trials, then more power to him. But I will be surprised if he does.