Half of them are saying, "Omg I knew it should have been them!" Shut up, you did not. You are not the next genius literature buff who made some mad discovery about a children's book. It was an obvious avenue that any author could have taken.
It was down to two options:
1) Make the lead end up with the female lead
2) Make the sidekick end up with the female lead
JK chose option 2.
Truth bomb that everyone really should know:
JK Rowling is a gigantic attention seeker. The fact we're all talking about it is proof in the pudding that she's succeeding at sucking all the attention back to her. She and all her retroactive "changes" (Dumbledore's sexuality being the first "retroactive" change) are part of a huge cry for attention. We get it JK, you want attention. We know you're going to "rewrite the series" because you've decided your heart could not live with the decision you made 3 years ago about the ROMANTIC fate of your leading male character. Of course that's the motivation. It is CERTAINLY NOT because no one cares about your new books, and you're desperate for another 15 minutes, right?
Regardless of whether or not you think she's a great writer (I for one, do not know enough about her to judge), I can absolutely say she's got 0 integrity when it comes to her OWN creative decisions. I can't respect any author who does that. You're fine to regret them but seriously?