Unlike Spock the audience are not telepaths. If he had a change of heart we should have seen it.
want movies to spoonfeed you, and to have the writers and director remove all such ambiguity from important scenes? That leaves very little to discuss afterwards except perhaps how did the creators do?
It's fun to ponder why and how characters do particular things. In real life we often don't know what's really going on in a person's head, and we must interpret from his or her actions. And we may well be wrong.
I guess you hate those episodes of CSI when the screen fades to black but not everyone has received their comeuppance?