More thoughts on Ron...
What if Harry and Hermione (and Neville) all get their 5 OWLs? What if Ron doesn't? Or, what if he gets 5 OWLs, but not in courses that he'd need to qualify for Auror training?

We've seen that Ron and Harry are both relatively indifferent students, but Harry found himself motivated toward the end of this 5th year. This is not to say that Ron wasn't -- after all, we don't know the contents of Ron's "what have you planned for your future, young man" conversation with McGonagall. But Harry has a natural aptitude in DADA; he seems to do okay in Transfigurations (and Charms, yes?); we saw him make an increased effort in Potions... That leaves Herbology and Astronomy for him to take a 5th Owl in. I'm discounting Divination and Care of Magical Creatures because McGonagall seemed to indicate that they were "gut" courses. That leaves, uh... Arithmancy (neither Harry nor Ron are taking it, right?); History of Magic (another possible 5th OWL); Muggle Studies; and Study of Ancient Runes (have either Harry or Ron taken this class?)

Hermione, I would imagine, would pass Potions, Arithmancy, DADA, HoM, Herbology, and everything else.

Neville would squeak by in most classes, including Potions. JKR made a point of noting that Neville seemed much more relaxed during the Potions exam than he usually was during Potions class.

Draco would also make 5 OWLs, allowing him to taunt Ron about something other than his Quidditch skills, his prolific family, or said family's lack of funds.

Ron -- let's give him a pass in Charms, Herbology, and DADA and a fail in HoM, Transfiguration, and Potions. That leaves him to make up a 4th in CoMC and and a 5th in Divination. So maybe he'll get 5 OWLs, but not those that would allow him to pursue a career as an Auror. Might the number of OWLs he got (or didn't get?) disqualify him as Prefect for sixth year?

If Ron's career options are narrower due to his OWL results, I'm envisioning him having a few resentful moments wondering whether Harry's status as "TBWL" garnered him unearned points when OWLS were scored. Plus, I think Ron would, as a result, also be jealous because Harry and Hermione would be thrown together that much more, (to his exclusion, a la Harry's resentment of Ron and Hermione's Prefect duties). Meanwhile, Hermione's proved to be Ms. Guidepost/Voice of Reason, and I think Harry's going to be listening to her take on things (like the status of houselves, for example, a position for which Ron, seemingly, still has little sympathy.). This may leave Ron, rather than Hermione, as odd-person-out when it comes to arguments, attention to schoolwork, and such.

I also can't help but feel it's significant that Harry and Hermione having the end-of-year-saving-Hagrid's-brother-adventure while Ron played Quidditch. It might just be significant in the sense that JKR has realized that male characters tend to get to do the more exciting things/hold the higher positions of power in the books and OotP was just remedying that. OTOH, it also might be another indication that the power balance in the threesome has shifted from Ron-Harry to Harry-Hermione.

Throw in Ron discovering that he was second choice as Prefect (and/or Harry being named Head Boy in 7th year) and you have a recipe for very bad feelings. And Ron has been showed to have a resentful nature, though he's always managed to overcome it in the past. JKR could even be really mean and have a rising first-year prove to be an awesome goal keeper, sidelining Ron.

Except for the latter, I do actually think that JKR has prepared the groundwork for these potentialities.

Hmm...